My son has white deep pigmentation around his mouth it started when a doctor gave him steroid cream to treat cold sore. He is 3 what can I do to help?

Correct info? First of all, are you sure it was a cold sore and secondly, are you sure it was a "steroid" cream? True cold sores are caused by the herpes virus and steroids actually spread the virus. One also has to be careful what one uses on 3 year olds regarding topical medications. I would discuss these matters with the doctor who prescribed the medication or check with a dermatologist.