Get enough rest. We know, we know, we're starting to sound like Mom. But, you know, maybe she was on to something. Maybe that's why doctors say that the quickest way to heal, is to let it rest. Avoid getting too cold.
Muscles react differently when they are cold.
That's why you see runners in sweat suits before a race. The same goes for throat and vocal cords. If they get cold, the possibility for temporary or permanent damage is increased. A recommendation is to wear high-collared shirts, turtlenecks, or scarves, during or before a performance. Especially, if the performance requires you to sing outside in cold weather.