due to the increased risk of bleeding it is possible to get what is called acute compartment syndrome while on
warfarin. this would be bleeding under the skin that cannot be seen but swelling is evident. this can press on nerves and cause function problems of hand. it is usually only if trauma occurs. and would only be on one side if the trauma was on that side.
however, i don't think this is the case. it sounds more like edema due to heart failure which is common in persons of that age and should be managed by the doc.