Hello I appreciate your concern Looking at your description this could be due to infection of the head of the penis may be due to STI or infected ulcer may be due to trauma during rough sex or an allergic reaction. I would like further information to guide you better If possible upload a photograph? do you feel any burning sensation in urine or increased frequency Your age and relevant medical history like diabetes or other metabolic disease Any recent exposure to unprotected sex? You should ask your doctor for few investigations to confirm the diagnosis like Urine culture and sensitivity test and VDRL test. Maintain good hygiene Wash and clean it with antiseptic solution or soap You can apply antiseptic ointment externally. Use condom during sex Neosporin powder can be sprinkled upon the clean site Hope this answers your question please feel free to ask for more clarification Thanks and regards