See the 'Restore a built-in app that you deleted' section in:
Delete built-in Apple apps from your iPhone, iPad, or Apple Watch - Apple Support
The first (and simplest) thing to try if something isn’t working right is to restart your Apple Watch and its paired iPhone. If necessary (device not responding), try a forced restart. Both methods can be found here:
How to restart your Apple Watch - Apple Support
Restart your iPhone - Apple Support
If that doesn't help, the next steps would be to unpair and pair your watch again and restore from the backup just created. This should result in no loss of data. It deletes all temp and corrupted files and re-indexes the file system.
Unpair and erase your Apple Watch - Apple Support
Set up your Apple Watch - Apple Support
As a last resort, follow the above procedure for unpairing and pairing the watch, but do not restore the backup. Set the watch up as new instead. There should be no loss of Fitness data or Awards since those are stored on the paired iPhone, not the watch.