Stress and anxiety can cause you to grind your teeth or clench your jaws. This condition is called bruxism, and often it happens as people sleep. In addition to creating a dull headache or a sore jaw, severe grinding can cause teeth to become painful or loose. This can lead to fractures in your teeth. Your dentist can fit you with a mouth guard to protect your teeth during sleep.
If stress is the cause, try to find a way to relax. Physical therapy, muscle relaxants, counseling, and even exercise may help reduce tension.