Hi Harrison123. Welcome to the forum.

I am not a doctor.  However, I am a bloke and I a little bit of knowledge. 

Most lumps on the testicles are harmless. There is also a structure at the top of each testicle called the "epididymis" which might be felt as a small lump. It's possible that this is what you've found.  However, Sweetpea1980 has given you some very wise advice: see you GP to discuss the lump.  It's probably nothing, but better to be safe than sorry, and your GP might be able to give you some more helpful information about how to check your testicles and what to look out for.

i know this is almost 2 years on but i recently started checking my balls for lumps etc,

Ive felt a sensitive lump at the top of my right testicle but not on my left. I've been to doctors and they've said it's most likely just your epididymis as it's sensitive and not painful but i can't feel it on my left side.

Can the epididymis be different sizes? 

Thanks :)

I'm not a doctor but bearing in mind the poem about the old man from Devizes  :happy:, I think it's quite possible for these parts of the male anatomy to be different sizes.

I am suffering from same symptoms I think It could be Epididymitis

Epididymitis is where a tube (the epididymis) at the back of the testicles becomes swollen and painful. It's often caused by an infection and is usually treated with antibiotics.

If the testicles are also affected, it may be called epididymo-orchitis.

Check if it's epididymitis

Symptoms of epididymitis may include:

sudden or gradual pain in 1 or both of your testicles (balls)

the bag of skin containing your testicles (scrotum) feeling tender, warm and swollen

a build-up of fluid around your testicle (a hydrocele) that feels like a lump or swelling

You may have other symptoms depending on the cause, such as difficulty peeing, or a white, yellow or green discharge from the tip of the penis.

I started checking myself out too, I discovered I have this lump too on my right testicle, on the top. I cannot find it however on my left one, my researches have lead me to "epididymis" which is a natural thing? Part of our anatomy? I have been rolling both my testitcles like it shows on the guide, I can't feel any lumps or bumps on the side of any of them, just this soft lump on the top of my right testicle, when I squeeze it, it feels just like squeezing the testicle, it's tender, glad you went to the doctor, I will do that too, but I believe it's the epididymis and nothing to worry about. I watched a YouTube video that it said that it's normal to feel those lumps on the bottom or the top of a testicle, they're the epididymis. Thank you for sharing this. 

I started checking myself out too, I discovered I have this lump too on my right testicle, on the top. I cannot find it however on my left one, my researches have lead me to "epididymis" which is a natural thing? Part of our anatomy? I have been rolling both my testitcles like it shows on the guide, I can't feel any lumps or bumps on the side of any of them, just this soft lump on the top of my right testicle, when I squeeze it, it feels just like squeezing the testicle, it's tender, glad you went to the doctor, I will do that too, but I believe it's the epididymis and nothing to worry about. I watched a YouTube video that it said that it's normal to feel those lumps on the bottom or the top of a testicle, they're the epididymis. Thank you for sharing this. 

Just a quick update: I went to the GP about a week ago now and he was very attentive, asked me to put pull my trousers down and he began to examine and squeeze my testicles, it took 2 minutes, he said there was nothing wrong, the lump is nothing to be worried about as it's likely to be an epydimal cyst, which is very common amongst men. I asked about it and he said it's not known how these things come to form but it's a harmless cyst, maybe it's been with me for years and I've only realised now and the "aching and discomfort" is due to my worry and from constantly squeezing it when the daily squeeze should be 2-3 times a day. I asked the doctor how he was so sure it wasn't testicular cancer, he said he had done his medical in his home country and he had to diagnose and deal with patients who were unfortunate to have develop testicular cancer, the lump is hard/solid and it's attached to the testicle, the Epydimal cyst is soft, choil-like tube and is not attached to the testicle, it also can't develop into a cancer, he said if I wanted to have a peace of mind, he could get me into a clinic to run checks, I've also had a urine test at the GP which he said they would get in contact if anything was found(nothing was found) after that appointment, I was more relieved, wasn't feeling pain in my balls, everything was super cool because I was really assured and if the lump was abnormal or something new, he would've sent me for a scan, but it's not always too sure so I should get it proper checked in a clinic, but doctors take a serious oath and they wouldn't play with a patient's health, me knowing that he studied and have dealt with this issue, gives me more faith in him. Some time later now I started to worry about the lump again and began squeezing it and the pain have started again, on both testicles it feels like an aching sensation, and also a dull belly sometimes, never any sharp, sharp pain. That's probably of being nervous, and from constantly squeezing it as it's a sensitive part of our anatomy. I will go to a clinic and run actual tests and update you guys more on it.

a long time ago I've also done the exam where they insert a robotic wire through the tip of your penis all the way down to the scrotum I believe, and that was to check something else completely irrelevant to this. I believe they would be able to see if any abnormalities was forming, nothing was found, all clear as well. 
 

I really hope this has brought some peace of mind to someone who's reading this because our brain do really take us to places and google also doesn't help at all. However, don't only take my word for it, have it checked with a GP as they're doctors and are trained professionals and would know how to differ a serious lump to one who isn't.