I noticed a dry patch of skin that went around right under the head of my penis. I thought it may have been dried semen so I rubbed it off after a shower and the affected area was very raw afterwards. I applied jock itch cream for 2 days and the skin stopped looking dry so I stopped. few weeks later I came out the shower and dried my penis with the towel and after I looked at my penis I seen that I may have rubbed it too hard and rubbed more skin off from the same area. Is this a std?