If you forgot your Apple Watch passcode
If you forgot the passcode to your Apple Watch, you'll need to reset the watch and set it up again.
How to reset your Apple Watch if you forgot your passcode
Put your watch on its charger and keep it there until you complete these steps.
Press and hold the side button until you see the power button in the upper-right corner of the display.
Press and hold the Digital Crown until you see Erase all content and settings.
Tap Reset, then tap Reset again to confirm.
Wait for the process to finish, then set up your Apple Watch again. When asked, restore from a backup.
Erasing all content and settings erases all media, data, and settings from your Apple Watch, but it does not remove Activation Lock. To remove Activation Lock, unpair the watch first. Before your watch is erased, a backup of its contents is created on your iPhone.
How to reset your Apple Watch using your paired iPhone
Keep your Apple Watch and iPhone close together until you complete these steps.
Open the Apple Watch app on your iPhone, then tap the My Watch tab.
Tap General > Reset.
Tap Erase Apple Watch Content and Settings, then tap it again at the bottom of the screen to confirm. You might need to enter your Apple Account password.
For Apple Watch models with GPS Cellular, choose to keep or remove your cellular plan:
If you want to pair your Apple Watch and iPhone again, keep your plan.
If you don't want to pair your Apple Watch and iPhone again, remove your plan. If you aren't going to pair with a different watch or iPhone, you might need to contact your carrier to cancel your cellular subscription.
Wait for the process to finish, then set up your Apple Watch again. When asked, restore from a backup.