I have a bump on the back of my head, what is it?

On the back of my head. It's hard and doesn't hurt. It feels like my skull but I've felt other people's heads and they don't have it. Is it normal? I've bumped my head there a couple of times but its been there for as long as I can remember. Can someone give me info on what this could be and if its normal?

Mama Mia2012-11-09T18:31:26Z

Everyone doesn't have a perfect head shape , it is usually just hidden by hair. You could have had an injury during birth, particularly if you were a large baby or very premature. it can also be an irregularity where the sutures of your skull knit together after birth. later causes or skull irregularities are falls and cysts that form under the scalp, like sebaceous cysts.