He's not liking having to share his attention and his possessions with this new interloper
You need to make him see that good things happen when the puppy is around
Giving him attention by himself is only cementing the fact that he will have to SHARE you
When you play with the puppy include him
Bring the puppy into the room and give him lots of treats
and when he's being "nice" keep telling him what a good boy he is