lump on child's head

I shaved my 20 month old son's head 3 weeks and 4 days ago and noticed a weird bump on his head that he has never had before. I figured he had bumped his head as children at his age are clumsy. So I figured it would go away but it hasn't it hasn't gotten any larger that I notice but am starting to get a little nervous. It is maybe a bit bigger than a dime and it is skin colored and right above his left ear it, it is hard to the touch. He was born prematurely and has had numerous medical challenges but has a clean bill of health.

[jmom3]

2 of my children have had something like that. It is like a small ball under the skin. The doctor said it was a fatty cyct and my daughter's was removed as an infant because it was by her eyebrow. My son has one on his neck and is only noticable when he looks to the side and turns his head. The doctor said it is fine and not in a bad place. If your childs is growing or changing colord you defenitally need to take him to the doctor. Hope this helps.