As Karla and Margot have already told you, if your puppy has never been bitten by a rabid animal, you have absolutely no fear of your son developing rabies even though your puppy has not yet been vaccinated.
Ghilly
Agree with Karla. I doubt, if the puppy has been with you for any length of time and not exposed to other animals, the risk of Rabies would be very low.
However, I might be a bit concerned about infection and would keep the scratched area cleaned and monitor it for any swelling and redness, etc.
How long have you had this dog? More than 10 days?
Has your puppy been bitten by any wild animal? If not, he couldn't have rabies! Nor could your child! Karla