Brief Answer:
Possible tendinitis.

Detailed Answer:
Hello dear, welcome to Ask a doctor service.
I read your query and here is my advice.

I think you may be suffering from tendinitis, inflammation of the tendons. It can happen as a result of over usage or injury. Possibly repeated movement like writing or playing.
Putting a bandage or stint on it to immobilise it us useful.
Also you may need to use antinflamatory drugs such advil or acetaminophen for pain and inflammation.
Also you can use warm and cold compresses to stimulate circulation.

Hope I have answered the question.
Let me know if I can assist you further.

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