You can delete the mistaken workout then enter a new one?
Apple Watch series 9 watchOS 10.1.1
You can delete or edit the mistaken workout from Apple Watch? I forgot to end a workout
Apple Watch Series 9
Apple Intelligence is now available on iPhone, iPad, and Mac!
Apple Watch series 9 watchOS 10.1.1
You can delete or edit the mistaken workout from Apple Watch? I forgot to end a workout
Apple Watch Series 9
As far as I know, you cannot edit a workout but...
To manually add a workout (and its data):
Be aware though that this only effects your 3 rings on the day in question.
Also see:
How to manually add a workout in the Health app - Apple Support
To delete a specific Workout:
On the paired iPhone tap the Fitness icon, then "Summary" in the lower left corner. Then "Show More" in the Workouts section. Swipe left on the Workout you want to delete and tap Delete.
You can delete the mistaken workout then enter a new one?