SFLA, it's really the same thing that happens sometimes when a child gets another sibling. They see it as a threat to their position in the house. The dog understands he's getting less attention because of the puppy and his role of being the house baby is over.

As long as he's not fighting the puppy, just give it time they'll eventually even start to play with one another. My German shepherd didn't like the shih tzu when he first moved in. But over the course of several months, they became more tolerant of one another and start to like each other. Now they're at the point where when I send one of them to the groomer's, the other one cries all day. So things do change.

Just make sure you give both dogs equal attention and treats. And the dog treats should be of equal sizes too. I made the mistake of getting my shih tzu a small bone before and the german got a large bone (which was the size of the shih tzu). After the small dog saw the other dog's huge bone, he didn't want his tiny bone. He wanted the big one and so he took it.