Many possibilities: Including trauma and infection. If it has persisted more than a few days get it looked at by a dentist. If it is brand new, see if it settles down fairly soon but if it lasts for 2 weeks, you really need to get it evaluated professionally.
Answered 9/25/2013
4.9k views
4 doctors weighed in across 2 answers
2 doctors weighed in across 2 answers
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