Tooth broke off: Gap. (photo)

Although it is hard to say without examining your tooth with appropriate X-rays,  there appears to be decay in your tooth which is probably why it broke.  You should see a dentist as soon as possible to determine the best course of treatment.  It may be as simple as a filling, or as comprehensive as a root canal and crown.

Steven Goldy, DDS

That tooth broke because there is decay in the tooth. That's also why the tooth hurts. You need to see a dentist who can remove the decay and put a filling there. Try to do this as soon as you can. 

Judging from the size of the break I would recommend a dental crown on that tooth. You may also need a root canal but that will have to be determined by the dentist With a x-ray. If you do not address this area soon it will only get worse and cause more pain and cost more money.