Canker sore under fresh tongue piercing?

I got my tongue pierced last week and it has been healing very well. I have been obsessively following the aftercare (brushing my teeth with soft bristle brush, saline solution after ingesting anything but water, and non-alcoholic mouthwash in the morning and at night). I noticed this morning what appears to be a canker sore under the ball on the underside of my tongue- could this be indicative of a metal allergy, or is it a standard part of the healing process? It doesn't hurt, but it is a little red/inflamed. I get them frequently as I am allergic to lots of things. Help!