Android Lollipop comes with stock notifications over the lock screen. you can safely disable them and continue using NiLS to show your notifications instead.
- Go to Android Settings
- Choose Sound & Notifications
- Scroll down and find When device is locked option and change it to Don't show notifications at all
If you want even better experience - it is highly recommend to enable Auto Hide Service on NiLS main settings page. this will take care hiding NiLS when on an alarm clock, on incoming phone call, etc..
It is also recommended to enable Hide on outside tap option on NiLS Interaction settings. this will hide NiLS whenever you tap anywhere else outside of the notifications list. to show it again, turn off and then turn on the screen again.