I Have A Bump On My Head That Has Been

I have a bump on my head that has been there for at least five, maybe six or seven years. It has slowly grown every year. It is a little smaller than the size of a dime and raised, but it is hard and I can kind of move whatever is inside around under the skin. At least it feels like that. It is not painful to the touch, but if I have a headache, I can feel it there. I attribute that to it being close to the location where headaches normally occur and a little bit of paranoia. Other than that, I don't usually notice it. It is on the top left of my head and not discolored at all. It only looks like raised skin. I vaguely remember itching it about 6-7 years ago when it felt like a mosquito bite and making it bleed a little. I have wondered if that is the origin of the bump. Thanks