Sometimes they go below the gum line for certain reasons.
I just had an upper bicuspid done, and crowned. The back of mine was tender too. I used a rinse once a day called Peroxyl.
It took down the inflammation quickly. Also where they stick the needle when they numb it can hurt for a while too. That area of the mouth is pretty sensitive because of the nerve bundle under the nose. So there may be some nerve agitation too.
Have you tried some Anbesol or Oragel on it? That might help a little too.
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Weezie looking at petunias 8.25.2017
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