What Causes Brown Marks On The Penile Shaft?

I have these brown dots/marks on my penile shaft.i am 100% positive i got them from masturbating way to muchhh.but all that aside.wat exactly are they? I am sure they were caused by friction.but they don t hurt.and never did.Every thing iv googled doesnt match up to wat i have.also they are seemingly permanent.iv had themfor over a year.is there some cream i could use to make them go away? They arent dangerous im sure.but unsightly.thanks for any input docs