A filling is necessary to treat your cavity because if left untreated the decay will eventually grow and will enter into your nerve canal. And yes, this can be as painful as it sounds. It can also lead to more serious problems such as infection or abscess. A filling may also be needed to replace or repair an old worn down existing filling or to fix a chipped tooth. In addition to potential pain and discomfort and possible tooth loss, if you wait to have your cavity filled it may end up requiring a more difficult process, such as a root canal, to save your tooth. And it could also cost you a lot more money to fix. The bottom line is you should get your cavity filled as soon as you can.
In some cases, our dentsit are not to perform extractions and will have to refer the patient to an oral surgeon.