Is there nudity?

Yes. There's video and photos showing everything, both male and female, front to back, top to bottom, nothing is left out. There's a lot of foul language and drug use as well. Not exactly your typical "family" type of movie. Most definitely not for kids.

Your main message says you "don't know how bad it is," but your topic sentence just discusses nudity (which I assume the "how bad it is" is referencing). You should probably bear in mind, this film shows plenty of "non-family friendly" parts that have nothing to do with Courtney Love's boobies. Is that really a deal-breaker for you?

Courtney's asymmetrical, pre-plastic-surgery areolas are a potential deal-breaker, but all the heroin use, suicidal ideation, Kurt's profane journal rantings, and rather graphic detail of sex with a mentally-challanged teen while he was a teen (possibly a euphemism for sex with Courtney) are alllllll gooood with you and the fam? It is really certain flesh exposed that nullifies it as "a family-friendly" flick?

Is this a troll post? Because when I think of a Kurt Cobain docu-special for the fam to sit around the hearth to watch, I don't think, "man, this film is 'a-go' until I hear partial fronal nudity for X-amount of seconds!"  

Nudity is the least concern! It isn't appropriate for family viewing at all!

There's nudity in everything

If you look at the parent's guide on this site, they have details about violence, nudity, profanity, etc.