You should never tolerate a dog that will growl or bite. I usually start when they are 6 or 7 weeks old. Feed them or let them have a bone then when they are interested in the bone or feed tug a little on their tail. When they growl or try to bite grab them by the nape of the neck, lift them off the ground and say no in a growling voice. Once or twice of this and they will never try you again. You don't hurt them but you sure train them. If they are too big for this handling then grab the muzzle and squeeze a bit and also say no and growl at them. You must always be the alpha!