Hi Rachel_H. Welcome to the forum. Please note that I'm not a doctor.

I noticed a bump on my wife's head about 2 years ago. We went to the doctor and she referred her for an X-Ray. The X-Ray came back ok - it was just a bony lump.  It wasn't until later that my wife recalled she'd previously (about a year or so earlier) received a hefty bash on the noggin int the same place as the lump from an open cupboard door.

Headaches and congestion can be caused by sinus problems. I should know since I've suffered from them for over 40 years (and right now, as I type this). Sinus problems can also cause some vision problems, too. 

I suggest you return to your GP and talk through all your symptoms. Say you're worried and ask what tests would be possible to set your mind at rest - but then PLEASE DON'T PANIC because suddenly you've been referred for the tests you've asked for (it does happen!). 

I suggest you phone your GP surgery tomorrow to make an appointment. Put everything down in a short note so you don't forget anything.