See the dentist immediately. By that time you can try this:
Rinse mouth thoroughly with a salt water mouthwash two to three times a day which may help to relieve a toothache caused by a crack or break. Salt water works as an antiseptic to remove bacteria from the infected area.
Apply clove oil at the site of pain using cotton swab.
Elevate your head when resting, some of the pressure in the area of the toothache may diminish.
Use an over-the-counter pain relief medicine.