Hello,
Without examination, confirmation of a diagnosis is tough but it can be contact dermatitis,rash due to friction rub, folliculitis, cysts ,molluscum
depression or plug) or genital warts(caused by HPV infection). Syphilis is a sexually transmitted infection caused by Treponema pallidum. The symptoms start with a sore which turns into an ulcer, which is called a chancre. The chancre heals spontaneously after 4 to 6 weeks. Your symptoms are not suggestive of syphilis.
Apply warm compresses, Neosporin ointment and calamine lotion and avoid messing with it. You can take anti-inflammatory pain killers like ibuprofen
persist then it will be best to get it evaluated from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.