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I would recommend that you have your doctor evaluate this as there are many possible causes. If there is a collection of pus, called an abscess, this may need to be drained by inserting a tiny needle and draining any fluid that is causing pressure to build up and pain. In order to know for sure what this is, your doctor will need to evaluate and help relieve the discomfort.
This article may be helpful and please let me know if you have more questions.