What causes finger stiffness and painthat last all day?

Need more info: There is no short answer. We need to know where, how often, how long you've had the pain. What kind of work/hobbies you do. How's your health.

Maybe trigger finger: It's hard to tell without knowing exactly where the pain is, but trigger fingers or arthritis cause what you are describing. See a hand surgeon who can examine you and get x-rays. Good luck!