Welcome and thanks for your question
I would be pleased to help you with your Question
What he seems to have got is a white patch
due to the application of the steroid
. It will take some time for it to resolve . most of the lesions resolve on their own . HOwever the duration of the wait cannot be predicted.
I would suggest you to meet a Dermatologist
who would prescribe certain pigment stimulating medication creams.
Thanks and Takecare