That sort of sounds like the factory reset prompt screen. This comes up of you have rebooted a few times (can never remember how many times is needed) and nickel has not been started successfully. But, it should have a question and buttons to press to continue or do the reset.
If there are buttons showing, you will probably need to do a manual factory reset. The instructions are at
https://wiki.mobileread.com/wiki/Kob...ing_squares.22.