While the stitches are in and everything, keep him clean ! no dirty walks, no baths until the wound is completily healed and the stitches are gone.
Don't let him play outside when it's wet or in the dirt etc., it can cause infection SO easily.
I know it's soo hard to ban the pup to play outside with the others etc., but it's for his own safety
Just play lots with him inside instead, play tug-of-war or let him find toys and treats around the house.