Hi
Apple does not offer a screen repair or screen replacement service for Apple Watch and Apple Watch is not user-serviceable. Your watch will instead need to be replaced.
Apple's Limited Warranty covers issues due to defects in materials and workmanship, but not due to accidental damage. Arrange service (see below) to establish whether your issue is covered under warranty.
If you have previously purchased AppleCare+, then the issue may otherwise be covered as one of up to two claims for accidental damage, each subject to a service fee / excess. Otherwise, your Apple Watch may be eligible for replacement via chargeable, out-of-warranty service. Prices in the US, for example, are detailed here:
Apple Watch Service Pricing - Apple Support
Contact Apple Support (mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider to arrange for your Apple Watch to be inspected and to establish your available service options:
- US: Apple Watch Service Answer Center - Apple Support
- Elsewhere: Select your country for Apple Watch service and repair information
In the meantime, note that Apple advises that you should not continue using a damaged Apple Watch.