Thelma-Louise

Chances are it is decay or a cavity since it only seems to hurt when you bite down on it which means food may be getting into the hole and causing some pressure. A tooth that needs a root canal generally will ache not only when eating but other times as well - like changes in temperature, when brushing, even just talking. Also it takes a lot to get the nerve of a tooth to die or become infected - usually only trauma from an injury or accident or untreated decay that has been there a very long time and did invade the nerve or canals can cause it. So its best to see the dentist and have it taken care of as soon as possible. In the event the tooth does need a root canal - not all rc's are painful or traumatic - seeing a dr that specializes in them such as an endodontist can make the experience no more painful than having a cavity done.