I have had a lump on the top center part of my head for around 7 months now that hurts very much when touched,it seems to have spread out on both sides like a tree branch.I suffer from severe headaches and constant pressure.I have gone to a Dr. and he said it was a cyst without even looking at it.I have also been to the ER and they took an x-ray and said that they couldn't find anything.I had a very bad fall around 4 years ago.I fell backward and hit my head first,was knocked out and when I came to,I was totally paralyzed,I couldn't even talk.The only thing I was able to do was move my eyes.Around 5 min.afterward I was able to get up.I believe that I had a concussion because I was seeing spots,flashes,and different colors for days.I feel this may play a big part in the lump.
This lump can be something harmless like sebaceous cyst, or benign scalp tumor (2% of all skin tumors appear at the scalp), but, very rarely it could be something more serious.
I don't think it is related with your head injury since the bump has occurred years after the accident.
The true answer can be given when examined with MRI.
There are chances the headache you have is due to a lump, but it is more likely to be side effect of the head injury 4 years ago.
Read about post concussion syndrome, that may follow after a mild head injury (concussion) and it's main symptom is long lasting headache that may appear days, months or even years after the head injury.