Root canal failure should be immediately brought into the consideration of the dentist that did your RCT. Dont try any medications prior prescription. You can try some home remedies like:
Soak cotton dipped in two to three drops of clove oil and 1/4 teaspoon of olive oil
Apply a dab of vick vaporub on the outside of the cheek where tooth hurts. Place a paper over the pillow and lie down on that side.
For more info on such topic visit the link....http://www.identalhub.com/article_home-remedies-for-dental-problems-88.aspx