We've had our 6 month old puppy (lab/collie/something with a curly tail mix) for 3 weeks now. He's a rescue from Romania and hasn't had a family before - was born in the shelter.
He has become what would be considered nippy in a younger puppy but in a 10kg dog is hurty 
Any ideas on this? It is mostly when he is excited or I am walking down the stairs. We will be starting classes shortly but I don't want any more nips. Have tried lots of treats when not nipping, getting him to sit when he is nipping to stop him and yelping like a puppy (no effect!)