Hello I share your concern, I had gone through your question diligently and I will try to help you out in best possible way Such a swelling on frenulum can be caused by infection , Sexually transmitted infection and can be allergic as well If you can upload me a photograph and answer my these questions I will be able to help you better Your age and relevant medical history if any like diabetes or liver disease? Have you ever had similar problem in past any recent exposure to unprotected sex? since I can t physically examine which gives more clue to diagnose you more accurately So,In my opinion you should see your doctor for physical check up and investigation to rule out infective condition Meanwhile you can apply antibacterial or antiseptic ointment like mupirocin Maintain good hygiene you can take Ibuprofen for pain. Hope this answers your question, Please feel free to ask for more clarification, I will be happy to help you Best wishes Thanks and regards