Pain in my fingers from practicing too much violin?

Try taking longer breaks and stretching everything out while you are resting (this is just a good idea in general, so you don't get overuse injuries), make sure you aren't clenching the bow (are there new bow techniques in this piece that you don't normally use?) and ask your teacher if he/she notices you doing anything odd with your bowgrip on the Viotti, make sure the leather grip on your bow isn't wearing (maybe you are getting too much pressure somewhere, could it be a nerve thing?), could always see a hand specialist, but I would try that last. My guess is that you are either tired, or are getting a little stiff on a difficult section without realizing it...it doesn't always take much. Try relaxing your left hand more too...usually what one hand does, the other does as well.