Concern about bump on head

I am 21 years old and am a little concerned about a rather mysterious bump on my head.  My mother actually noticed that there was a bump on the right side of my head that hadn't been there before.  I simply assumed that I may have hit my head sometime back and that's what caused the bump since it is hard like a bone and doesn't hurt at all.  Its been several months since we first noticed it and hasn't changed in size.  It is just above my hairline on the right side.  I am not having any symptoms that I would assume are associated with it like headaches or blurred vision or something of that nature (which i read from other people and their experiences).  I was just wondering if I should be worried about it...  Thanks so much.