I have a slight dent in the middle of my head. should i be worried about this?

We are imperfect: If the dent has always been there and not bothersome to you, no need to do anything. Based on where it is, hair is covering it and so no one would notice. Most, if not all, of us have some imperfection here or there which makes us unique, at least physically. Some we can cover, some we can't. As long as you are content, that is all that matters. If you have trouble, consult doc. Good luck.