How long does a jellyfish sting last?

I was stung by a jellyfish on my forearm, in Folly Beach, South Carolina around the beginning of August of last year ('10). There is a medium sized scar that I've been told will be there for the rest of my life. Rarely, but often enough, I may feel a tiny sting where the initial sting was. When I was stung, protocol was followed and, we believed we removed all the toxin from the area. Is it possible to still feel an occasional tiny sting, in a larger vicinity after almost a year after being stung?