Hi, I Had A Permanent Retainer For A While On

Hi, I had a permanent retainer for a while on the back of my two front teeth and about two weeks ago one side came off of my tooth instead of taking it off I left it alone. The next morning I woke up to a big knot behind my two front teeth and its sore to the touch. However now its starting to turn a little bit of a white color and almost favors a blister. I'm a little scared because my dad passed away five years ago with mouth cancer. What should I do?