Denise,
You are very lucky nothing happened to your little dude.
These little ones have such an attitude (one of the reasons I love them) and they will go after anything in their territory or the whole world for that matter. Many a little Yorkie was killed because of this and all it takes is for a big dog to pick it up by its neck and shake it. My little Bella 3#'s thinks nothing of going after any big dog and running up to them and bitting them on the nose. Thank goodness she is only doing this to Sammy (a lover) who is a 14# Yorkie (?) but Moose at 4#'s is the same way. He goes insane when the big dogs walk in front of my house and I know if I let him out he would be dead. I am always amazed at their courage or stupidity
when they do this. Just be a good mom and protect him from himself.