It is important to see a dentist. There are a few possibilities, but if the tooth broke, possibility number one is that your tooth may have a cavity which caused the healthy enamel to get soft and weaken the structure, leading to a portion breaking. You also could have a fractured tooth which when pressure is applied during chewing, leads to more pain. You will need a few x-rays and the pain could also come from having a larger cavity that has reached the nerve and you tooth may be dying. No matter which possibility you should see a dentist, if untreated you could experience constant throbbing pain, or swelling could occur if your tooth becomes infected. You have a chance to at least try and save your tooth, but waiting it out is not advised.

Yong E. Park