First, clean and wash the wound gently with a quaternary soap like normal (regular) Lifebuoy soap and water fifty times.
Do not cover the wound as the rabies virus dies on contact with air.
Did the dog bite without provocation? Can that dog be identified and tied up for observation for ten days?
If he bled from the wound, then it is a Class III bite. Please arrange for Post-exposure Rabies Vaccination. The new vaccines are given in a small dose intra-muscularly in the arm or thigh. Anti-Tetanus Vaccine may also be given if your son's normal immunization schedule has not covered it.
He will require a painkiller. Please consult your Paediatrician.