Justin Bieber: Sobbing Was Real�Jitters Got Best of Me

Justin Bieber wasn't crying crocodile tears ... he really did get choked up and overcome with emotion when his VMA gig ended, and he's blaming his nerves for the sobfest. Sources at the award show tell TMZ ... the Biebs was super nervous before his big "What Do You Mean?" performance ... because it's been five years since he last sang at the VMAs.