9 weeks is very young to have already left his mother. They learn most of their socialization skills from their litter mates and mom up to 16 weeks. When they leave too soon many times it will result in inappropriate play and behavior issues.
But growling while playing with a toy is normal. At the same time I would be worried about the social skills that will not be learned since he is way too young to be away from mom.
__________________ “Never argue with a fool, onlookers may not be able to tell the difference.”  Mark Twain |