If reports are correct and it's his left elbow that needs a "precautionary" x-ray, then I'm not too worried. Really the main risk in an elbow is dislocation, and he wouldn't have been moving his arm after the crash if he'd dislocated it.
I suspect he has some swelling and soft tissue damage and they're just being safe. IIRC he used both arms when climbing out of the car, so a fracture is very unlikely.
Fingers crossed he can race tomorrow.