Before you leave, there are a few things you need to do. If an adult tooth has come out completely, try to reinsert it. Never try this with a baby tooth, as you could damage the adult tooth under the gums.
If you are unable to push a knocked out adult tooth back into place or you have a fragment of your broken tooth, store it in milk. If the tooth is dirty, you can rinse it with water first. Do not scrub the tooth nor use any chemicals and avoid touching the root surface. You can also wash your mouth with water and use a gauze to apply pressure if there is any bleeding. If the broken tooth is due to an impact with your face, use a cold pack to reduce swelling.
A broken tooth can cause nerve damage, such when a crack that extends to the pulp. In this case, you will most likely need root canal therapy. This involves drilling through your tooth (or whatever remains of it). Your dentist will remove all the damaged pulp to stop the infection spreading. You will need to return later for a crown or filling to seal the top of the tooth.