Are there foods or habits to avoid when my jaw hurts?

Yes, there are. For foods, avoid 1) tough, chewy items like dried squid, beef jerky, and galbi (ribs), 2) hard nuts and ice, and 3) gum that requires long chewing — and while you have pain, cut soft foods into small pieces before eating. For habits, it's best to avoid 1) opening your mouth wide (support your chin when yawning), 2) resting your chin on your hand, 3) chewing on only one side, and 4) sleeping face down. However, if pain persists for more than 2 weeks despite adjusting your foods and habits, or your mouth opening becomes limited, you should come in for an examination.