How To Cure A Depression On Skull Causing Concussion?

I am 19 years old, 5 7 , and 130 pounds. When I was 8 years old, I had taken a hard floor with my head hitting the concrete floor. As far as I can recall there was no bleeding, but I after looking back now I could swear that I suffered a concussion. After the fall I felt light headed and dizzy, then when I went to bed I was starting to vomit. I was never taken to the hospital despite my symptoms. Now I realize there is a large depression on top of my skull and it concerns me that it will become a problem. It feels softer than the rest of my skull when I press on the area. If I actually had a concussion and it was not treated, how did I not suffer any brain damage? I don t experience that many migraines nor headaches.