Which version of XeLL has the NAND got on it at the moment?
Build a new image for your console (JTAG/Glitch), rename it to updflash.bin and put it on the root of a FAT32-formatted USB stick.
Boot your console to XeLL with the USB stick connected and tell us what happens.
For future reference, DO NOT modify/delete ANY files from the Flash:\ partition unless you know what you are doing.
In fact, disable the Advanced File Manager view in FSD and then you won't be tempted to mess with any files there .