Severe tooth pain is usually caused by deep decay or infection affecting the tooth's nerve. Try rinsing your mouth with warm salt water to soothe the area and keep it clean, and avoid chewing on that side so the pain does not worsen. Applying a cold pack on the cheek can help reduce pain and swelling, and stick to soft, lukewarm foods while avoiding very hot, cold, or sugary items. Keep the area clean by gently brushing to prevent food from getting stuck. If the pain becomes constant, spreads, or swelling appears, consult a dentist soon for proper treatment and lasting relief.