If you haven't done anything, then you have nothing to worry about. The BON would investigate each claim but if there's nothing to find then they will dismiss. If it happens enough times even they will start rolling their eyes when your name comes across the desk again...not at you, but at whoever is doing this to you. If it can be shown to be vindictive, there might even be a charge of filing a false report to the complainant.
documentation and witness's are very important. If you are staying within nursing quideline you have nothing to fear. I see you work in a jail. Inmates make sport out of suing people. Just follow the rules and you will be fine.
No, this isn't a documentation problem, this is a former 'friend', who turns out to be psycho, who is now threatening to 'go after my nursing license', because it's a hot button for me....and this individual would lie, cheat, steal or sell their Mother's soul to get whatever they want...(sigh)
Document this "conversation" with the psycho. As soon as s/he files any type of complaint, get an attorney and sue, seek an injunction, file a criminal complaint; whatever your state law allows.
Wacko's, freaks, and bullies only cause trouble for people when the risk/reward ratio is to their benefit. Aggressive self defense will normally deter a nutjob from further mischief.
If all else fails, you can always take out ads (for several concurrent weeks) in the newspaper classifieds: EARLY SUNDAY MORNING GARAGE SALE - EVERYTHING GOES BEFORE CHURCH! (use the psycho's address: every garage sale junkie in town will start banging on his/her door at 4am!)