The backlight on my iphone 6 won't turn off

[iMore Question]

The backlight on my iphone 6 won't turn off. I've clicked on auto-lock and changed the timing, I've turned the phone off and on and I've pressed the home button/on and off button but the backlight still stays on. I've only had the phone for a week and I updated to the ios10 so I'm not sure whether its been doing this only since updating to ios10. Should I reset it and start again.