It is not unusual to have some sensitivity after a deep dental cavity is excavated and filled(restored). If the decay which was removed was too close to the pulp of the tooth, it is possible that the nerve has been injured and infected by the bacteria which caused the decay. If the decay had been on the side of the tooth for a year or two, it could very easily have extended far enough to have affected the pulp. That is why we recommend dental checkups every six months or less. Decay found at the six month intervals usually does not extend to the pulp unless there are other factors present. Call your dentist and explain that if the pain and swelling are getting worse.