Although not a licensed physician, some hand/finger exercises that work for me are the "spider/mirror" pushups (place each finger on its respective counter part and press together, as if doing a pushup.). Repeat stretch 5 times.
Then, the thumb extension (with thumb extended, rotate thumb backwards with opposite hand pressing towards thumb wrist, be gentle, you can overdo it and injure yourself). Repeat stretch 5 times.
Then, thumb curl, (place opposite hand on back of thumb and press towards thumb palm. Hold for several seconds.). Repeat stretch 5 times.
Then, individual finger stretches (use opposite palm to bend individual fingers backwards until you feel a stretch in the finger pocket. You might hear a knuckle crack. Do not overextend. Repeat stretch 3 times.
Hand massage helps relieve pain. Curl one hand into a loose fist and use the other hand to gently massage the back of the fist hand. Repeat for opposite hand, 2 to 3 minutes each. Massage hands often including during performance breaks. This helps stimulate circulation and helps keeps your hands warm. Wearing fingerless wool gloves also helps keep your hands warm until showtime.
If your hands or fingers hurt after a performance, be sure to ice them down for 20 to 30 minutes, then the following day, apply moist heat. Then, do stretches as normal. If your hands/finger hurt before a performance, you may find your evening may be less than stellar. If possible, do not exacerbate any injury by subjecting your muscles to additional strain during recovery.