Hi
Cosmetic damage, including scratches, is not covered under the One Year Limited Warranty or AppleCare+.
Your watch may be eligible for chargeable, out-of-warranty service. Contact Apple Support (mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider with a view to having your watch checked and to establish any available service options, likely timescales and cost: