I have a small skin colored bump on the shaft of my penis, but if I pull the skin taught it looks like a zit and begins to appear white (as if there is pus in it). It is hard, I have tried to pop it several times, but no such luck. It has a small crater in the center of it, as if it was an ingrown hair, but usually those infections are possible, and there are only very miniscule hairs on the shaft of the penis.