J'imagine que « se mêler de » désigne le fait de fourrer volontairement et indûment son nez dans les affaires d'autrui qui ne se regardent pas.
In this sentence, I opted to say "fourrer son nez {stick your/one’s nose}" to refer to the generalised/indefinite you, but then I found myself struggling to keep the pronouns consistent throughout.
As much as I want to say "qui ne se regardent pas {which do not concern you}" in keeping with the "on/son/se" consistency, the "se regarder" could easily be mistaken for its (reciprocal) reflexive verb usage with the meaning of "look at each other" or "look at yourself".
So what is an ambiguity-free alternative for finessing the situation? Swapping in "tu/ton/te" or "vous/votre/vous" doesn’t sit well with me.