A few days ago I noticed a soft lump on the back of my head on the lower left side. It has a dull pain. I've been having bad migraines for the past couple of months also

Did you talk to your doctor about this?

Time to see a doctor.

Please consult the doctor as soon as possible!

A knot that is not explained on your head with headaches? So many possible issues. You should see your doctor ASAP