How old is he? Sometimes birds that are going thru a "teenage" stage get hormonal and moody. Otherwise like someone said. Probably just moody. Whatever you do don't back down to him. You need to remain the boss. Even if it means putting on a set of gloves. If you show fear and pull your hand back he will get it in his head if he acts nasty you will leave him alone.

__________________
Koda-my best friend, don't tell my husband, he thinks he's my best friend..lol