Light sensor not working after Lollipop update After upgrading my Nexus 5 to Android OS version 5.0 Lollipop, an issue has occurred: light sensor doesn't work properly when I am trying to call someone. Screen always stays on and I am not able to have a proper conversion, because I accidentally touch the screen with my cheek and, for example, mute my microphone...

Would factory reset help me solve this issue? Or maybe you have any other tips on how to solve this issue.
This is an issue with lollipop and it has been reported to google. Until google fix the issue you need to lock screen using power button manually.