A Few Weeks Ago I Had A Small Siz Scab

A few weeks ago i had a small siz scab ob my head..i scrtched it off which left a quarter size bald spot ib my head. Now the bald spot has increased in size to about 3 inches in diameter and it looks like there is a dark spot forming in the middle of it. My hair has not grown back yet..what is it? Will my hair grow back? Should i go the hospital? Is there aimething that could help? Im a 31 year old caucasion female.