I feel for you! I know about Novocain - I have had two root canals and last week I had gum grafting surgery, which I am still feeling the effects of! Anyway, the knot might be a sore or a tender spot leftover from the needle going in. Those needles they use for Novocain are the most obscenely long and humungous needles I have ever seen. It might also be residual tenderness in your mouth because of where the work was done... for example, I have a bruise on the left side of my face because the grafting was done on the left, so it affected that entire part of my face. The mouth is extremely tender and sensitive, and it almost goes into trauma after serious dental work. It takes time for it to return to normal, but if you feel like something is not right, it wouldn't hurt to call your dentist's office and ask just to be sure. After my root canals it was a good 7-10 days before my mouth felt normal. I know you didn't have that done but you still had a serious procedure. Good luck and feel better soon - I know that mouth pain is the WORST!!