Hi
Apple advises that you should not continue using a damaged Apple Watch.
Apple does not offer a screen repair service for Apple Watch. Your watch may instead be eligible for replacement via chargeable, out-of-warranty service.
Prices vary by model and region. Apple's out-of-warranty repair 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 establish your available service options, timescales and cost and to arrange service: