I think it's a conure thing. Our mitred did the same thing. We have a two and half year old blue crown now. He hasn't drawn blood yet, but he will display lots of aggression before he softly chomps down. I don't test it when I see that he would bite if given the chance.
I accidently taught him "OUCH!" My dad isn't happy with me, but when I saw the beak coming, that's what I said. Now he says it sometimes when he is displaying, or if he drops one of his toys hard on the floor. Once he was playing with a toy roughly against his feet, so I told him ouch. He looked up and agreed, "ouch," but went back to playing hard anyway. He also sometimes plays with people, tickling their ears, or fingers, not looking aggressive, but he will go a little harder and harder. When he sees them flinch, he then proudly says, "OUCH!"
I am trying the, "No ouch," approach, but yeah, I still think it's a conure thing. Sometimes it's a game, but most of the time, it's a wild animal territorial, moody thing.