A couple days ago a hard pea sized lump developed on my penis, it was hard most of the time but could become a little softer with massaging . The lump grew over night and it stayed the same for two days, it then began to decrease in size. The day after its first notable decrease in size , it looked like it had crusted over , and left a harder skin there , perhaps a scab I can't particularly tell. I'm not sure if this is a simply a benign phenomenon or if it is an std.