My left upper gumline started to swell about a month ago. I have an old root canal there. Now the pain has spread to the roof of my mouth & the nose. 2 weeks ago my front upper teeth have become sensitive to hot / cold and the gum & lip there sometimes swell. The pain shoots up to the nostril, especially when I wake up. I had teeth whitening done by a dentist about 6 – 7 months ago. But everything was fine then. . . and no side-effects then. Could it be gingivitis / tooth abscess (due to old root canal) or side-effects of teeth whitening (had it done for the 1st time 7 months ago) ?????????