Rectal rash

Patient: My 2 year old son started out what looked like a diaper rash. we tried over the counter diaper cream (corona) but it did not work. Then we went to a clinic that prescribed him desonide cream. it has not worked. now the rash does not look like a diaper rash. his rectum has a ring around it that is pink and raw looking. what could this be?

Doctor: