My baby Baylee had the same problem. Its more than likely just the fact that the puppy is teething. I remember Baylee's smelled awful!
Just make sure you brush the puppy's teeth and give it lots of chew things like hides and ropes to play with.
My Baylee is a year and a half old and just had to have one of her baby teeth pulled out surgically yesterday. Her top left canine was retained and we had to get it out before it rotted the other teeth.
I suggest you try and watch the teeth as they fall out and get an early jump on loosening those canines so that you dont have to have them surgically removed. Its no fun!
