[JoeyP]

You need to explain what it was and what type of behavior he was showing in order for anyone to tell you if it was aggressive or not

Puppies esp active guys like Yorkies will tend to play rough sometimes
and just like with a toddler you have to train them what is acceptable behavior and what is not

What works with puppies better than putting them on their back because I'm a little afraid.... knowing my guys when they were puppies if I did that they would have thought that was a game

When puppies get rough you need to come in and with a loud stern voice say NO!
and then all attention and play ends right there
and if the behavior is esp bad you can do the same with a little neck grab
which means you take the skin by the neck .... and you do this just gently enough to pull them away
You do not need to be forceful with this

But it is important to stop this before it becomes a permanent part of their behavior