Since the puppy is vaccinated, there is no need of any treatment for your son. But make sure that the puppy has received anti-rabies vaccine
. If it has not then you need to give the anti-rabies vaccine to your son. It consists of 4 doses given intradermally on days 0, 3, 7 and 28. If the bite wound is large then stitching should be done after 48 hours and a course of antibiotics is necessary because dog bite wounds are highly infected with microbes from the dogs saliva.