Concussion, broken clavicle, probably other smaller injuries too... there's not much info out just yet (not that I've scoured the 'net).
He's not going to make the Nationals for a little while, probably will miss at least the first race and probably the second I'd guess. Though Nationals are staged two weeks apart, he'd be an amazing healer to get well enough to be back in four weeks. You can't splint or pin a collar bone AFAIK, it just has to heal and you have to leave it alone and not move it at all: no riding.
This is a huge shame b/c the outdoors was shaping up to be one hell of a series. It would be the comeback of all time for him to miss two races (and by that I mean four motos) and still be in the title hunt.
The important thing is he heals completely;he doesnt want injuries to do to him what happened to Pastrana.He's already proven hes the best 125 rider out there.......missing this years championship is less important than being healthy for future seasons.