It has been 3 weeks since root canal was started, i have a temporary crown over it. the area has been hurting pretty bad. the dentist said to wait.

OK: No question asked. Infection? Antibiotics? Swelling? Your dentist knows more about you and this tooth than you've posted. Let the dentist know you have discomfort.

Pin in root canal: If your root canal was started and you are still in pain 3 weeks later their is a problem. You need to be seen by your Dentist because that is not normal. There could be a few different reasons, however the Dentist needs to address your problem. So get in to see him or her! Good Luck!