My baby has thrush and I brought him to the doctor yesterday when I noticed it and they gave me…

My baby has thrush and I brought him to the doctor yesterday when I noticed it and they gave me nystatin for it 4x a day to put the drops in his mouth at the cheek and I started last night and then this afternoon I noticed red dots and his cheeks raised red rash on it and the chin so I called the on call for his pediatrician and the doc said just to stop the medicine and if it doesn’t clear in 24-48 hours to bring him to the office to be seen. It still makes me nervous that he has had an allergic reaction to this medicine...I will be watching him very closely tonight