Hi, I ve realized a few days ago that I have a scab on my penis. It s gotten bigger & darker within the days & I m starting to get worried. I masturbate regularly without any lubrication & shave on a weekly basis. I have no other scabs, sores, bumps, etc on my shaft. I ve tried putting Neosporin on it to see if maybe that would help, but hasn t done anything. Is this a form of an STD? Should I just let it heal on its own or take precautions, such as see a doctor?