Being possessive over a person, food, or play toys will lead to major dominance problems in the future. In these situations, you will need to take over the job vacated by his dam and teach you puppy manners in a way that he will understand. The best way to correct dominate or aggressive behavior is to make your puppy submit. Look down on him and keep him restrained until he stops fighting you. It means that he is thriving both physically and mentally.
Socialization can never be over stressed.
It is you responsibility to see to it that he is introduced to as many new situations as possible. Of course, make sure that he is protected with proper inoculations first. Then, the sky is the limit. Take him for a walk in the neighborhood. Go to the woods or the beach.