Apple watch blue box on the top left corner of the screen

This is not a defect with the watch. The blue box is caused by AssistiveTouch. To turn it off, open Settings > Accessibility > AssistiveTouch. Toggle it off.

It looks to me like you have the Metropolitan watch face. See the 'Metropolitan' section in:

Apple Watch faces and their features - Apple Support

and see what complication you have set for the upper left corner. see the 'Add complications to the watch face' section in:

Customize the watch face - Apple Support

(Could it be the Camera Remote?). In any case, try to change it to something else and see what happens.