IAYM, I've had gum pain for a day or two after a root canal, but never after just having a filling. Was the filling on the chewing surface of the tooth? If so, it might be that the dentist built it back up too high. Even the slightest bit higher than it should be can cause that tooth to impact on it's opposite tooth before the surrounding teeth do, and cause that tooth to compress further than the surrounding teeth. I've had this happen before, and it can cause quite a bit of pain, until the dentist gets in there and takes down the high spot.
Definitely, go see your dentist, and have him check it out. If it's something simple, great.......and if it's not, better to get it fixed asap, right? Good luck!
