I would try a spray bottle with water(don't let him see you with the bottle and don't spray him in the face). It worked for me for a while. They will grow out of it. Just redirect them to a chew toy when they start nipping. Don't let anybody play rough with him either this will only encourage his behavior. I can tell you it doesn't get any easier. I have a 10month old GSD and he's insane. I have him on NILF. He has to obey a command anytime he gets a treat. Don't get me wrong I love him to death and will never give him up, but it has been a really difficult breed to deal with. Here is a link to an all GSD board
http://www.germanshepherds.com/ubbth...ubbthreads.php
Good Luck!