mommamia22-
One thing that makes any parent feel sad and powerless is hearing their child say that they have no friends.
I agree with the other posters who suggested that you invite the other child over to your house to play with your son.
Perhaps adding an excursion to the pizza store, or making homemade pizza, can serve as a further enticement for a play date.
Also, do you have any nieces or nephews he can play with?
Hatzlocha raba.