What Could Cause A New, Painful, Golf-ball-sized Hard Lump Above My Ear?

I have a large lump on the side of my head. It is hard, not squishy, above my ear, not warm or discolored, but painful to the touch. It is larger than a golf ball. Not caused by a fall or injury. Tenderness noticed a few days ago and lump noticed today. What might it be? Should I call my doctor?