According to your symptoms, it is most likely to be a rash
due to prolonged pressure. Please watch out for other symptoms like itching, burning sensation, discharge or spread and take proper help from your health care provider if necessary. In future try to wear only cotton underwear. Ventilate the area well. Apply some olive oil or calamine
lotion if it is a contained rash caused by the pressure, to obtain relief. You may also wash with mild antiseptic solution. Hope you find this information useful. Wish you good health.