Hi,
If the scratch is annoying you, you can get it fixed under the accidental damage as far as I'm aware.
On Apple Watch series 5 however, this comes with an excess of:
Apple Watch Series 5 service pricing – United Kingdom
Out-of-warranty service fee
Apple Watch Series 5 (GPS) (Aluminium) £286.44
Apple Watch Nike Series 5 (GPS) £286.44
Apple Watch Series 5 (GPS + Cellular) (Aluminium) £326.44
Apple Watch Nike Series 5 (GPS + Cellular)£ 26.44
Apple Watch Series 5 (GPS + Cellular) (Stainless Steel) £376.44
Apple Watch Series 5 Hermès £376.44
Apple Watch Edition (Titanium) £476.44
Apple Watch Edition (Ceramic) £756.44
I'm presuming this wasn't a manufacturing defect? If you think it was, please contact Official Apple Support who might be able to help you make a warranty claim if they find it to be a defect but as it doesn't inhibit the functionality of the device, I am unsure what they'll be able to do.
Please see this link for more information:
https://support.apple.com/en-gb/watch/repair/service/pricing
https://www.apple.com/uk/support/products/watch/
Hope this helps
[Personal Information Edited by Moderator]