Tear a piece of cotton cloth wide enough to reach from under your arms down to your hips and long enough to wrap around your body comfortably once. An old cotton sheet is ideal (never use nylon or polyester). Dip the cloth into cold water, then wring it out. Wrap it around your middle and secure with a large safety pin or two.
Now wrap a thick dry towel around this and lie down, or even better, climb into a warm bed. You might want to put on a pair of thick socks so your feet don’t feel cold. Rest for at least half an hour. If you do this just before bed and you drop off to sleep for the night, that’s ideal. You can always remove the compress in the morning.