When the wrong size of catheter is being used, it kind of hurts/burns for the entire time that it is in the vein. So if that is what you're experiencing, that could very well be your problem. Or it could be a mild allergic reaction to either the remi itself or even the catheter itself.
I am allergic to latex, so my nurse uses vinyl gloves and paper tape, but I don't know what the catheter is made of. I always have a tiny rash around the injection site for a few days afterwards. Do have a rash from it, too? Or just the burning?