Google Nexus 5 :: Bootloop From Root App Permissions

I'm not really and expert on flashing stuff on Android. I was pretty comfy not rooting my phone for more than a year. TBH, I didn't really need it, because I was not a power user, but I've recently installed a root app called King User (King Root, etc.). It made things easy for the very few apps I could not use without root permission. However, when I received the latest OTA (5.1.1. security update) I had to disable root authorization in order to install it. So I disabled it using the app's built in authorization setting.

The OTA update failed and gave me the error with the opened up android and the red exclamation mark. So I thought that the app messed something up. Disabling in house did nothing. Uninstalling it did nothing. So I decided to replace it with SuperSU using this guide: [URL] .... After SuperSU deleted KingUser and updated itself the phone remained stuck inside a bootloop. So I figured this replacement process messed up permissions.

My bootloader is locked and I have no custom recovery (because like I said, I just needed temporary root access for a couple of apps and wanted to avoid the hassle). When I enter Recovery mode in default fastboot it gives me the "No command" error (probably because of SuperSU permission).

Now I don't even know if the phone is rooted or not. USB debugging was not enabled last time the phone was on and now I think I'm stuck in this point where nothing works without something else. Doing a full recovery now would probably be asking for a lot, but right now, I would be happy if I could just do a factory reset or something...