How To Treat Dark Spot On Side And Head Of Penis?

Hello Doctor, I have recently developed a darker spot on the side/head of my penis. I haven t been sexually active in 4 years but it has occurred since I have been masdurbating, I didn t use lubricant or anything all the times that I did, so I have a feeling I have answered my own question. It is like a burn, darker coloured skin circling a bright pink patch where the skin has rubbed. I masdurbate differently by massaging the tip rather than grabbing it with my whole hand and this has occurred where my fingers rub. I ve had this for months now and I have masdurbated at times when I ve had it but I need some help besides stopping masdurbation for a while, I can do that, but does it just heal on it s own or is there some cream I can put on it? Could really use some help! Thank you.