I Felt Slight Soreness On The Top Of My Skull,

I felt slight soreness on the top of my skull, front right side, and noticed there was a lump, approx .5 to .75 inch wide and .25 inch high. It was sore like a large acne would feel. The next day the soreness was entirely gone but the lump has stayed for 4 days now. It is hard like bone. No pain or other symptoms. It occurred suddenly. One day there was nothing and then the next day it was there. Please help.