When did you get the crown placed? If you had it done in the last couple of days, you may have something called as a 'high point' on the crwon, because of which you have the pain. See your dentist immediately and he/she will remove the high point. If the treatment is not recent, then you have to get it evaluated by your dentist. An x-ray might be taken. If root canal has not already been done, and the tooth is infected, the crown has to be removed, a root canal done and a new crown placed (usually the same crown can not be placed as it has to be cut and removed). If root canal treatment has already been done and still you have pain, then the x-ray should show whether the problem is in the same tooth or any adjacent teeth.