Hello I share your concern, i will try to help you out in best possible way. Looking at your description this could be STI or infected ulcer may be due to trauma during masturbation or an allergic reaction. Another possibility is prostate problem or a Renal stone I would like further information help you better relevant medical history like metabolic disease or hormonal disorder 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 an ultrasound to see for prostate enlargement Blood for CBC and liver function test or urine test are advisable if it is a chronic issue Maintain good hygiene Wash and clean it with antiseptic solution or soap You can apply antiseptic ointment externally. Use condom during sex if you are sexually active Hope this answers your question please feel free to ask for more clarification Thanks and regards