I have a sore red rash on groin?

Infection: Sore (painful) red rash usually suggests soft tissue infection referred to as cellulitis. Best to go see your family doc for evaluation, diagnosis & treatment, usually antibiotics. In meantime, warm compresses can be used for infections while ice is recommended for injuries.

Rash: This can't be diagnosed with the information that is available. A history, physical examination & other studies may be needed to determine cause/causes. Once accurately assessed a treatment plan can be developed.