Sorry I meant to say as well, before my surgery 17yrs ago my jaw kept locking open as well and would only unlock once i woke up from sleeping. One day I took my hands and physically pulled my jaw closed. At that point I shattered my articulating disc.
How much would it cost to get panoramic x rays on your jaw?
For now until you decide to go to a doctor I would use a heating pad on your face and maybe see if you can get a prescription for muscle relaxants in your jaw.
did you have an overbite before? is that why they did the surgery?