Hi there,

You shouldn't worry. Mostly because you have no idea what the result will be, so what use is worrying? From what you've described, I wouldn't be too concerned but it's important you still go to your doctor's appointment to be on the safe side. 

Nobody here can diagnose you except your GP or a qualified dermatologist. Most likely, you're looking at something like a calcified insect bite or a sore which is just starting to heal.

As you've mentioned, there is a chance (a very small one) that it could be skin cancer. I assume the appointment you have is with your GP? They'll be able to give you an idea of what it is. If there's any doubt / concern, they will refer to you a dermatologist who can have a closer look.

Please know in the meantime that even in the worst case scenario, Skin cancer is very treatable when caught in the early stages. Many skin cancers (like Basal Cell) have an excellent prognosis / outlook since it very rarely spreads or does anything except grow on the skin.

So - long story short, no you shouldn't worry, chances are it's nothing, but it's still important that you see your doctor to make sure everything is OK. There is still a small chance and it's important you rule this out.

Wishing you a good dose of reassurance soon!