Not to worry you, but you may want to ask your doctor to evaluate you for rheumatoid arthritis. I have a friend who had symptoms similar to that and she ended up having the beginnings of RA.
I know this kind of thing happens to us knitters all the time, the thing that concerns me the most is the fact that its swelling. I've had pain and some issues of stiffness and redness before, but swelling is typically an inflammatory response in relation to an infection or injury. And swelling in joints can be attributed to RA.