Hello,
It can be due to chafing or intertrigo. Chafing occurs due to friction rub of skin with skin or clothes. Wash the area with mild soap like Dove and apply calamine lotion on the rash. Also do not use any cosmetics and wear cotton undergarments. Application of mild corticosteroid cream and oral antiinflammatories like ibuprofen/acetaminophen are also helpful.
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.
Using baby powder or hydrocortizone cream can hep with this rash. It is probably just irritated skin from being immobilized. Make sure you don't get any type of infection, but other than that these OTC things should help.