I went for root canal treatment and today i discovered swelling. my dr. says its due to the reaction af anesthesia.is it critical. m worried about it?

Local anesthesia: When we give local anesthesia, especially with an infiltration injection, the tissue may temporarily swell from the slow infiltration of the fluid. Less commonly, a hematoma may form which will take longer to dissipate. As long as the swelling is not from an untreated infection, you will be fine.

Relax: It is highly unlikely a reaction to the anesthetic. It's more likely swelling related to the trauma of the root canal. Reactions to the local anesthetic used by dentists are pretty uncommon. An allergic reaction would have occurred immediately, not this long after the injection.