There is a small black bump just under the head of my penis on the shaft. It only raises up when I'm erect or stretch the skin the bump cannot be squeezed for it is to deep. And when I try it just squeezes through my fingers. What could it possibly be?

Please see your doctor to have this properly diagnosed. It could be something serious or it could be just a wayward pimple. But don't guess, let the doctor take a look and tell you.