You are in for a rough ride so better buckle up. Without his littermates around to teach him what is/isn't ok you need to be the judge of that, in fair terms a pup that young can understand. He needs to be able to play bite something...better get a bunch of stuffy toys. His teeth are going to be hurting him as he starts teething and chewing is the only way to relieve the pressure. Give him tons of toys. If he bites you, put him in a crate or room away from you for a two minute time out. Then go back and play, play, play, with the toys that are Ok for him to have. At this age it will be a struggle to train him in any way. He has only been here for four weeks, he is just learning the lay of the land so to speak. You will have to be extremely patient with him. I don't want to sound mean but shame on your uncle for letting a pup go that young, he shouldn't be breeding if he doesn't know that a pup has to stay with its mom and littermates for at least seven weeks, perferebly longer. For training, I would only focus on teaching him what is Ok to chew on and what isn't and a bit of the old potty training. Save the hard stuff for when he is adjusted to your home.