Apple today released watchOS 9.5.1, a minor bug fix update designed for the Apple Watch. watchOS 9.5.1 is a free download that comes two weeks after the launch of watchOS 9.5.
watchOS 9.5.1 can be downloaded for free through the Apple Watch app on the iPhone by opening it up and going to General > Software Update. To install the new software, the Apple Watch needs to have at least 50 percent battery, it needs to be placed on a charger, and it needs to be in range of the iPhone.
According to Apple's release notes for the update, it includes "improvements and bug fixes" for the Apple Watch, with no details on which bugs have been addressed.
Source: Macrumors