It is normal to have some soreness as the teeth and jaw are getting used to moving. This typically resolves in a few days to a week.
Use some lip balm or Vaseline on the lips before putting your rubber bands on to help keep your lips from getting chapped overnight.
If the pads on the appliance get worn down, you can replace them with Dr. Scholl’s MoleskinⓇ pads that you can find on Amazon or at your local drug store.
If the skin becomes dry or irritated where the pads touch, use some lotion or Vaseline to help rehydrate. Using the Dr. Scholl’s MoleskinⓇ pads can help with skin irritation too.