I accidentally sprayed something on my eye and it's burning! What should I do to wash it out?

Rinse it out! As soon as possible irrigate the eye with tap water or an irrigating solution for a minimum of 15 minutes. You should also see a doctor asap to make sure that it did not permanently damage the eye.
Go to the E.R. If you have eye wash or are near a faucet, let the water pour into your open eyes. After 15 minutes, have someone drive you to the emergency room, where they can further flush the eye and ensure that there is no remaining chemical in, or injury to the eye.