A person's fingers may swell at night if they are holding their wrists in a flexed position. It may also be a symptom of carpal tunnel syndrome.
More than 100 different types of arthritis can cause soreness in the hands, as well as swelling, which can occur at night. For those that suffer from arthritis and other hand diseases, making an effort to keep the hands at a relaxed, neutral position, particularly when at a computer, can help reduce swelling.
It is also important to stretch your hand and wrist muscles on a regular basis, such as placing your palm flat on a surface, with fingers facing the body, and using muscles to pull your arm towards your body.