Luckily, the phone is water resistant so it should be fine. If there is a problem with the phone, then you can refer to the troubleshooting page on a way to fix it. Moto X Pure Edition Troubleshooting

If the scratches are not that deep, you can try to buff it out. If that does not work, then you should replace the back plate. If you need help replacing it, you can refer to the troubleshooting page: Moto X Pure Edition Troubleshooting