Our pup, Waldo, around 5 months, and still gets nippy. If he won't stop (or if it escalates!) when we say NO! he gets a mini time-out in his crate. We put him in, and hold the door shut for as long as it takes him to sit down (not pawing at the door or pacing) and then let him out (no more than 1 minute usually). Then he steps out, shakes it off and goes for a toy that we offer. But we definitely have our share of bruises and torn clothes from the past few months!