My 13 Year Old Son Has A Red Rash Size

My 13 year old son has a red rash size of a dime near corner of lip and a smaller red rash above lip on opposite side... didn't have time to see a dermatologist because we leave for DC on the 15th but our pediatrician presribed Triamcinolone acetonide... it appears the rash is drying out becoming darker and scabby... pediatrician thought it was a reaction to something but not sure what... my question is at what point should we be concerned that it is something different and see a Dr... we are going to be in Wash DC 15-22. The rash was noticed on June 9 and started to apply the cream on June 11.