Lock icon with circle ios7 need to unlock

Slide up the new Control Panel window from bottom of screen. There you should find a similar icon in the upper right, lightly shaded white. Tap on it and it will turn grey, removing the little icon on your screen and unlocking the screen.

Hope this helps - worked for me, though how it got turned on in the first place a mystery...

I just had this same problem. I also accidentally open up the control panel menu all the time when I'm just holding my phone, so I can see how the button might have gotten pressed accidentally.

iphone