What Causes Stiffness And Tenderness In Joints Of The Fingers?

I recently developed sudden joint/knuckle stiffness and tenderness in my pinkie fingers on both hands and ring finger on left hand. I had been doing 8 hours of repetitive tasks with my hands immediately prior to these symptoms so I thought this might have been the cause...but now the symptoms have persisted for a week and a half later and I am concerned. The stiffness and tenderness have largely subsided in one pinkie finger but has seemed to worsen in my ring finger. Bending the finger and applying pressure to the phalange cause the most discomfort. Any thoughts on treatment and/or diagnosis?? I had been using cold therapy and ibuprofen for a while to reduce any inflammation.