When in doubt, always use ice.

When heat is applied, it increases blood circulation and in turn produces mild inflammation to the surrounding tissues. Typically when you're in pain, there's already some inflammation present. Applying heat in this case is like “putting fire on fire.” Even though it may feel wonderful, you'll pay for it in the hours following.

Ice, on the other hand, functions as an anti-inflammatory agent and natural pain reliever. You should typically apply ice at 20 minute intervals 3–4 times during the day. But you'll get the most benefit if you apply more frequently during the day.