I know of no medicine to make the node go down. Maybe an anti
-inflammatory might help a little bit. I assume the medicine
you were given is for the sore.
BUT!! if the canker sore and the node both result from autoimmunity, then a powerful anti-inflammatory like prednisone could help a lot. If the canker sore is from a bacterial infection, then an antibiotic should hurry things.
"Can it turn into something serious?