If you had pain prior to the preparation it is not uncommon to have pain after especially for the first few days. If it does not subside there may be other factors involved including but not limited to a fracture or crack, an exposure of the nerve, over prepping...If it has been more then a few days you should contact your dentist and let them know what is going on.
Any tooth that has pain before it is treated, certainly has potential to have more pain after it is treated. My assumption is that it had a crack or fracture in it. I would discuss the possibility of this tooth needing a root canal should the fracture be deep enough that it goes into the nerve of the tooth. However, initially, if I assumed that we were able to remove the fracture without nerve involvement, I may tell the patient that we are going to monitor the tooth for any signs or symptoms of nerve involvement including sensitivity to cold, biting, pressure, etc. It sounds as thought there is nerve involvement. You should contact your dentist and let him/her know immediately.