You haven't provided very detailed info, but I would suggest you get it checked out for scabies. It could also be a heat rash--have you been working outdoors or sweating a lot lately? Essentially, there are a number of possible causes. Take some benadryl and see a dermatologist.
This can be due to contact dermatitis, fungal infection or sweat dermatitis. Keep the area dry and after washing also dry thoroughly by pat drying, not rubbing. Also wear cotton underwear and change them twice a day and do not share other people’s towels.
Try any of the over the counter products which contain any of several basic ingredients: miconazole, tolnaftate, terbinafine,ketaconazole and clotrimazole. You can consult a pharmacist and get any cream or lotion containing these ingredients. If the symptoms are severe then oral antifungals may be needed.
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.