Thanks for the additional information. It is helpful. He really isn’t being aggressive so much as trying to solicit you to play with him. If he was with another dog, he would do this to try and convince them to play if they let him.
It sounds like he needs some obedience training to help him learn some manners. If he saw you as the ultimate boss, he would listen when you tell him to stop, lay down, etc. Right now he still thinks he can make decisions such as when you play. He has found that if he bites, you don’t ignore him and what he wants is your attention.
This can be corrected pretty easily with obedience training. It doesn’t have to be a formal training class but does have to be formal training sessions. It should also be done daily as well. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
This serves the purpose of obedience training him which is always a plus as you gain absolute control over your dog, but also establishes you as the boss and leader and dogs respect the boss and listen. They also do not act aggressive toward the boss in any way. When he goes to try and solicit you to play, you can command him to sit. However, the fact that you are spending a lot of time training him also gives him the attention he craves too. So you are accomplishing several things at once.
Long fast paced walks will also help cut down on his energy level and help tire him out. Now when he does attempt the bites or what I call mouthing, there is another way to help stop the behavior as well. You can stop mouthing and biting hard by going the opposite direction. Instead of taking your hand out of his mouth, put it further in the mouth. DO NOT do this meanly (not that you would). Do not do it quickly or shove it in too far, just move it further in enough that it makes him uncomfortable so that he pulls his mouth away from your hand. He will learn that putting his mouth on your hand results in the hand going further in and possibly triggering a gag reflex which he will not find pleasant. I've found that this methods works on the most stubborn puppies and he is still a pup.
I’d also try and find him a playmate that is the opposite sex and similar size and age. That will also help him get rid of excess energy and also learn not to bite too hard if he is currently. Keeping the playmate to an opposite sex dog will help eliminate fighting between the dogs. Also introduce them away from either home so they have a chance to get to know each other before being in one or the others territory.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer so I am compensated for my time.