Along with iOS 15.0.2 Apple has released watchOS 8.0.1 on Monday, which fixes bugs for Apple Watch Series 3 owners.
watchOS 8.0.1 Release Notes
- Software update progress may not be displayed accurately for some Apple Watch Series 3 users
- Accessibility settings may not have been available for some Apple Watch Series 3 users
It can be installed through General > Software Update in the Watch app on iPhone.