Watch app

That's why I said unpair the watch first,so you can then delete the watch app.

1.Remove watch from icloud.

On a computer, go to iCloud.com and sign in with your Apple ID.

Go to Find Iphone.

Select All Devices, then click your Apple Watch.

Click Erase Apple Watch.

Select Next until the device is erased.

Click the remove button next to your Apple Watch.

2.Force reset phone.

3.Launch the watch app,when it prompts you to update the watch,press accept and after it fails leave the app and delete it.

Are you trying to open the watch app or unpair the watch?.

Unpair the watch then delete the watch app and reinstall it then re-pair the watch.