Brief Answer:
Can be muscle strain.

Detailed Answer:
Hello,
Thanks for posting your query.
Given your age, the most likely cause of your pain would be a muscle strain. Muscle strain results from a stretch of the muscle during exercise or movement especially after a forceful turn or step. Management includes:
-rest
-use of ice
-compress the calf to prevent blood from pooling in the very acute situation
-use of anti-inflammatory drugs such as ibuprofen.
Other possible causes could be
-cramps
-Pain due to baker's cyst and
-blot clot.
You should try the above steps in order to manage the pain. Pain should be able to decrease within few days. However, if the pain does not reduce, or the calf swells or has color change or is red and you have a fever, you should seek medical help immediately.

I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Wishing you good health.
Regards.
Dr. Praveen Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Praveen-Tayal

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