Remember, dogs are pack animals, and your newe arrival must learn his place in the hierarchy.
Your old dog will feel unsettled with the new arrival. Oder dogs are usually patient with pups, but he may have a snarl or two to remind junior who is in charge.
As head of the pack, you must be sure that pup knows his place as well. make sure you fuss your older dog more than usual, especially give him some individual attention and stop the pup pushing in.
Your pup will soon adapt to the situtation, but as advised, be patient.