When you say he will not drive to the right, do you mean he will not turn in a circle(say, at least 20 meters dia.), or that he will not bend to the right?
If its the former, maybe grounddriving him, with a person at his head, in a large right hand circle would help. The person can keep him from going off track or wheeling around to the left. Eventually, the person steps away, as the horse gets comfortable with walking to the right.
I tend to say either pain or driver error. Not an injury caused by early work however, unless he was driven hard. But teeth are still a possibility, esp. if he is losing caps. Had a bit seat done? Changed bits, harness, driver recently?
I would not tie his head around, imo, it does nothing to aid you in getting him to go to the right. Consistent work to that side will do far better.