So, as of lately I've noticed that when I have an erection, I can feel this small bump under the skin on the shaft of my penis. Thing is, it doesn't move with the skin, it seems attached to the muscle of my shaft. It's fairly hard to grab, and when squeezed, which is hard to do because the skin on top of it moves too much, causes little to no pain. It's fairly hard to find when not erect do to the size difference of when I'm erect and when I'm flaccid. It's quite hard, almost like cartilage, since it can be squeezed, but requires a bit of pressure for it to deform. I'm fairly positive I have no STD's, but not too long ago suffered from a rare condition called Lichen Planus, which did appear on my penis only a little. I have had the condition fixed by a small dose of prednisone.