When must I call my doctor if I have malocclusion pain?

Never. A 'doctor' does not understand nor can treat a malocclusion or pain associated with it. Best to see an orthodontist-that is their specialty.
Pain? Not sure this is directly from the malocclusion, but i would see an orthodontist right away.
That would be now. Only a dental professional can determine if your pain is due to dental or periodontal infection, occlusal (bite) trauma from malposed teeth, or jaw pain (muscle or joint)associated with tmd. Call your dentist.
Agree. I agree w dr ali. Pain is your bodies signal that you need help. Don't suffer, call you dentist immediately. If he feels your pain is caused by malocclusion, misalignment of teeth and/or jaws, ask him to refer you to an orthodontic specialist.