I cannot confirm anything without examination but it can be dermatitis skin, contact dermatitis or heat rash
. Keep the area clean and apply some topical antiseptics. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove. Oral antiinflammatories like ibuprofen/acetaminophen are also helpful apart from steroid creams. If the symptoms are severe then it will be best to consult a dermatologist.