Extreme Tooth Sensitivity What Should One Do About Extreme Sensitivity On A Molar Tooth?

What should one do about extreme sensitivity on a molar tooth? - extreme tooth sensitivity

I had braces a year ago. When the key was to come, the key in the lower left first molar had to return twice. Close process involves a machine that turns away at high speed and tail. I felt a little sensitive after ignoring the second time, but easy. Now I have an extreme sensitivity in my left lower first molar. Near the gingiva of the tooth is sensitive to cold and touch. What should I do? Do I need root canal treatment?