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Since when are you having this pain?
Do you have cough
, breathing difficulties, fever
along with the current problem?
Did you sustain any injury?
Acute onset pain without any other symptoms is more likely due to muscular sprains. Adequate rest, local heat application, local antiinflammatory spray/cream application should make you feel better.
Discuss with a doctor/post here if there any updates with respect to the above questions.