Swelling and pain in fingers can be due to injury, carpal tunnel syndrome, and arthritis etc. Spleen is part of lymphatic system and filters the blood. It removes old blood cells and platelets from the blood. Its removal can lead to increase risk of clot formation causing pain and inflammation at the affected sight. There are chances that a clot has blocked blood supply in the pinky fingers of your husband and causing pain and inflammation. But it is not a final diagnosis. It will be good to see a doctor for proper investigations and treatment.