'if it continues you can bring him to a trainer'...
I go to trainers even when things are going well. And since puppies biting and growling are NORMAL to be EXPECTED and something almost all of us go thru.. sounds like you wanted a GSD, got a GSD, and then go what comes with it.
There is a reason we had to make a 'sticky' for this behavior our pups have so frequently. It's because this is how many of our GSD's play. PLAY. Not 'aggression' though blood may be drawn and pain is felt. And it may sound scary too.
When we select a breed, it's up to us to learn about the breed and deal with the normal breed behavior as it crops up. Patience (not to into the scruffing of puppies, and as they get bigger this won't work too well
) and TRAINING a new way to play tend to work best in the end.
With exercise and DOG CLASSES ! --> http://www.germanshepherds.com/forum/welcome-gsd-faqs-first-time-owner/188549-puppy-biting-hints-tips-help.html
You are in good company, many (most) of us have been in your situation and also had to work through it.
MACH3 Bretta Lee Wildhaus MXG MJG MXF MFB TQX HIT CGC TC
Glory B Wildhaus AX, AXJ, XF
"Behind every great man is a woman rolling her eyes." - Jim Carrey