If there is no pain and itching then these symptoms can be due to friction rub during sex. But if there is any pain then herpes blisters and STD’s and if there is any itching then fungal infection should be ruled out.
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.