That is not possible. Installing to "NAND" in FBI will install on whichever NAND you are currently running.
If you screwed up NAND injection, I recommend starting all over again with a clean sysnand (restore via gateway launcher, hold up while pressing A on downgrade console) and perhaps also update to 9.2 via sysupdater on RXTools 2.5 DevMode to make the injection consistent.
Also, make sure you go into Data Management to prepare sysnand/emunand for cia installation (but never go there after you initialize it, or you will delete everything!)
You don't need FBI injection on sysNAND. You can go HBL->PastaCFW->Start HBL again->FBI and use that to install whatever you want, such as a CIA of FBI. rxTools Pasta Mode (previously called Dev Mode) will also work in place of PastaCFW.