Remove square from lock screen

A forced restart fixes this issue.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN)

If a Forced Restart didn't make the box disappear, check if Larger Accessibility Sizes is enabled. Normally, the box should only appear when you press and hold the icons, but disappear again when you let go.

You can check if the feature is active here:

Settings > Accessibility > Larger Text > Larger Accessibility Sizes

If you still want to use larger text, scroll no further than the image.

Cannot remember the exact wording of the "tip"

Try hold your finger on the "box" and wait to see if a menu option appears that will allow you to remove it from the screen, so it will go back to the Control Panel where it belongs.

Try to restart your iPhone.