That's encouragement for him to dominate over you. He is at eye level on your shoulder and feels more in charge. If things don't go his way, he'll bite. That's what he does to his mate attempting to drive her back to the nest. The bird may also run behind your neck and bite you when he doesn't want to be put back in his cage.
Bites can be serious.
Often, owners walk outside with a bird on their shoulder, not realizing he's there. I t takes training to have him remain on your wrist. If a bird bites at wrist level or on your hand at waist level, the damage may not be as serious or as painful. It will take time until your bird stays on your wrist. You must be very consistent.