That is kind of strange behavior. I have had two huskies and two kids and neither dog has shown protective behavior over them or any of us, for that matter. I would guess (again, no expert) that he is perhaps a little insecure with the situation and is showing fear.
Since you have a child, that dog will most likely be around lots of children in his lifetime. I would take Riley's suggestion that you address the issue so he will not think that this is appropriate behavior around busy, loud and sometimes scary children.