An easy and important initial treatment that can be started (sometimes at the scene of the injury) is immersion of the injured extremity in hot water (preferably 110-115°F). The water should be as hot as the patient can tolerate but should not cause burns. The water should be exchanged for more hot water as it cools, for an immersion duration of 30-90 minutes.
That's the treatment the hospital down on Galveston Island, Texas uses for stingray strikes. I haven't needed it but two of my friends did (seperate occasions). The both bring chemical handwarmers to the beach with them now for this very reason.
-Blast