Possible trouble with lip ring?

Canker sores can be caused by any sort of mouth trauma (piercings, tooth extractions and other oral surgeries). As long as you are cleaning the area as you were instructed, it should go away in a week or so. if it doesn't get better or gets worse, you may want to have it looked at just in case you have infection (which is pretty common, considering how many germs are in the human mouth)