What Causes Moles On The Shaft Of Penis?

hi...over the last 4 years or so I've noticed a number of mole like bumps appearing on my penis. Some are flat and some are raised. I asked my GP about them and he said it's nothing to worry about. But one in particular is increasing in size and I notice that others are appearing. I'm concerned that eventually they may cover my penis. In total I've noticed about 6.