oldman_peter
the pain is real, but caused by muscle contraction/cramp as a reaction to a sensation. You've taught yourself to wince until it hurts, and now contribute the pain to external factors. You've come to expect the pain, so it'll hurt.
The mind trick is right there: understand that you cause the pain yourself as reaction to a sensation and be mindful in situations where it might happen. You will find that the pain is caused from expectation and habit, this knowledge will break the cycle. Keep it up a for a few months and you'll untrain your habit a great deal.
it's like fixing the way you drive your car
Consciously reprogramming your body is hard because often there's not a quick or obvious training/reward cycle and it takes time. You might not even know what to train or how, and even if you get detailed instructions you might have difficulty translating it to your body and how you would feel/experience it. I could explain how to twitch your ears, but chances are you're not even aware of the muscles that would allow that. A first task would be to become aware of a bunch of face and ear muscles and go from there.
Another example is when someone mentions your neck is all tensed up and you think you're all relaxed and chill. Over time you've hacked your body to recalibrate your feeling of being relaxed, to the point where you don't know to really relax your neck muscles. Hacking your body/changing behaviour takes time and conscious effort, and it really helps to be convinced that it is possible, or at least doubt that it is impossible to hack.