If the crown is a temporary crown it is not unusual to have some sensitivity or discomfort while in place. This can usually be handled with over the counter medications but can be bad enough a more power painkiller is needed. If the crown is the permanent crown and you are having discomfort several days after it was cemented there may be an issue with the bite (occlusion) of the crown or an issue with the nerve. If the bite is high, simple adjustment will take care of the issue. If the nerve is infected/inflammed there could need for root canal treatment to solve your problem.I would contact your dentist for evaluation and let them discuss the situation with you.