Herpes infection of the skin usually follows insignificant trauma to the skin. Pain, tingling
, redness and sometimes, swelling of the local area precedes the development of the rash. As your baby has no pain, I would re-think the diagnosis. I would suggest that you upload a picture of the rash and put your question again if you can.
In any case, the other possibility is that this is a fungal skin infection
, and for this one would need to apply an antifungal cream such as fluconazole
twice a day for 4-6 days.