Dental wax is used to cover the braces to prevent rubbing. These are easily available at most pharmacies. It is a soft mouldable wax that can be press over the areas that are rubbing. This will stop friction and allow the sore areas to heal.
Warm salt water is good to use but if it doesn’t work then go for 50% warm water with 50% hydrogen peroxide rinse for a couple of times a day; especially right before bedtime.
Visit your dentist if the problem still persists.