I Have A Bump On My Sculp Approx. 1/4" Off

I have a bump on my sculp approx. 1/4" off scalp and 1/2" wide. I press on it and it throbs. No visible sign of a ingrown hair. Noticed it after my head was pounding all day on the right side of my head in one small location. What could it possibly be a sign of? Im 20 yrs old