Contrary to popular belief, one can not squeeze orange juice or blood from the yoke. In older models, particularly the Cessna twins, the yoke had a habit of breaking off should the pilot grip too tightly. If you have another pilot or instructor on board, ask them to spare a second from fearing for their life to check on if your knuckles are white while doing a maneuver. If your knuckles are white, you're gripping too tightly.

There's a bunch of medical things that could be going wrong, especially if you spend plenty of time typing on a computer. Most will continue to hurt after the stressor is gone (i.e. releasing death grip on yoke).