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Lump can be due to various reasons as infection,abscess,lymph node swelling etc being the common ones.Usually they subside on their own in a week or so.If the size of the lump increases along with shape,consistency and worsening of pain or development of any other symptom then it is a cause of concern.Apply ice pack 3 to 4 times in a day.Keep self examining for any changes.
If the symptoms worsen or there is increase in the size of lump then it would require an evaluation.Usually CT scan is done to help in the diagnosis.
Take Care!