I have a knot on my head!? What should I do?

Its 5am and I just woke up and I feel this knot on my head. Its the size of a penny and doesn't hurt even when I touch it. Im very worried and scared because I didn't bump my head unless it was in my sleep but if I hit it that hard I would have woken up. Im 13 and live in georgia. I don't feel dizzy or anything like that. But please please please tell me if I might need to go to the doctor!