I am a 37 year old female, 5'5", 133lbs. I have a painless, hard, non-movable lump behind my left ear on my skull and under the skin. The bump itself is painless, but from time to time the back of my head feels "odd". The sensation is very hard to explain. The best I can describe it is the way I would expect to feel after I had a concussion. (However, I've never had a concussion.)