I have the same issue, pain behind my right eye. I'm a year post injury.

I'm not a doctor, so I could be wrong here, but my understanding is that it could be one of three things:
- referred neck pain
- eye strain being caused by some underlying visual issue, like convergence problems
- palsy/damage to one of the nerves that control your eye muscles

Have you had a full exam by a specialized optometrist or opthamologist?

I had an optometrist rule out any major issues (I did have convergence issues initially, which they think are now resolved) so in my case it's probably one of the first two things above rather than the third thing. But either way I'll be seeing a neuro-opthamologist to try to figure it out.

My eye pain is more pronounced if I look to the extreme left, or if I'm looking off to the distance. There's still something subtly off with my vision, I see everything sharply but motion still throws me off. It's a bummer because I still can't drive very much.