My pre molar feels tender after having a chewy sweet. I have had root canal on this tooth few years ago if that helps. Slightly hurts when biting down?

Pain. Pain is your body's way of telling you there is something wrong. May have failed root canal treatment. If tooth needs retreat net, best done by a root canal specialist, an Endodontist.
See DDS. Have the dentist evaluate the area to make sure that the crown, if your have a crown, is not loosened or that the tooth is not fractured.
Needs evaluation. Tooth may have a fracture, a recurrent infection, or even periodontal bone loss. Please call your dentist for an appointment.

Related Questions

I had a cracked molar that was repaired w/a root canal & crown dentist said I may always have tenderness on that tooth after biting&i amIs this valid?

Possibly. If the crack extends to the root surface it becomes more difficult to get the tooth completely pain free. A consult with an endodontic specialist can give answers and options. Read more...
Cracked Molar. If you continue to have pain on biting after a tooth has had Root Canal Therapy and a crown and you have allowed for sufficient time for healing, the long term prognosis is not good and you might want to consider extraction and an implant retained crown. Why be in discomfort and risk ultimate failure down the road? Read more...
Guarded prognosis. Treatment of cracked tooth syndrome is not always successful and the prognosis is always guarded. Your dentist should inform you about the prognosis and treatment outcomes. Read more...