Hi there. Sorry to hear you are in pain. Take the Advil, as suggested, as opposed to anything else. It has an anti-inflammatory property, as you may know. What has happened is that your cavity was most likely very deep and your dentist may have aggravated the nerve as a result of drilling near the pulp cavity. If you feel this way tomorrow, go back and ask them to re-assess the tooth. They will probably do a bite adjust, (just in case)and a possible open and drain, as it is called to relieve the pain. This is the start of a root canal, and it will help your discomfort. the only other alternative to the root canal is extraction. Kind of a poor prognosis, but there you go! Hope you feel better!