As soon as possible, apply cold to the injury on an hourly basis for 20 to 40 minutes at a time, depending on the size of the injured part. Cold constricts blood vessels, lessening bleeding and limiting swelling and pain, and it also muzzles those screaming nerve endings. Continue with cold therapy for at least 24 hours and up to 72 hours for large muscles. If it's practical, try to compress the injured part. This might involve taping a twisted ankle or applying an ice pack to a knee with an elastic bandage.
Compression also limits swelling, preventing the injury from raging out of control.
Elevating an injured limb above your heart also lessens bleeding and swelling by making the heart pump blood uphill, reducing blood pressure. Proper application of RICE will get you back in action quicker than any other strategy. It's not at all unusual to enjoy nearly complete recovery with three days. Some injuries, however, just aren't so easily vanquished. If you're still uncomfortable three days or longer after the injury, and if the swelling is gone, heat may help.