Try to give the area as much air as possible. Use baby powder or talc powder to absorb excess oil/sweat.
There are many OTC creams and ointments for heat rash available.
Hello,
One possibility for such a rash is fungal infection. Keep the area dry. Also wear cotton underwears and change them twice a day and do not share other people’s towels. I suggest you to get it examined from a dermatologist to confirm the diagnosis. If fungal infection is confirmed then you may need topical and oral antifungals.
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.