Thanks for the additional information,
Well this doesnt seem to be like a blood clot but rather more of a muscle spasm or spasm of tendons, this is because the movement of fingers seem to aggravate the pain. This can be caused by electrolyte disturbances especially in patients who are on medictaion for various disease such as you and also in patients in whom there is an element of dehydration. Now this can be treated with the help of rest, hot and cold compresses over the area and also by use of OTC painkillers such as aleve or advil.
Now the blood clot theory IS possible but is unlikely in the absence of any swelling, change in color or temperature of the region of the arm distal to the pain, the pain in blood clots is severe and excruciating. While you are prone to devloping the clots because of your age and the fact that you have arthritis plus fibromyalgia, from what you describe here it doesnt seem likely. Although a complete examination of the arm would be needed to exclude this condition as i cannot be 100% sure of this fact without an exam.
I would suggest that you use OTC painkillers and the warn compresses and see your doctor in the morning for an exam HOWEVER if you develop any of the following symptoms at any time during the night then you need to go to the ER immediately,
Swelling of the arm or hand
Change in color of the hand
Any increase in pain
I hope this helps
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