If it's an emergency just use lots of warm water. Test the water on your wrist, if it's too hot or too cold adjust it until it feels comfortable. That way you know it'll be safe for kitty. If you have some dish soap a little of that wouldn't hurt either, just make sure your rinse it out thoroughly.
Why do you need to rinse it out? is it causing an irritation to your kitty? If it is I would also schedule a vet appointment, just to make sure it doesn't get worse/become infected.