stick (one's) nose (in) where it's not wanted
To involve oneself in an intrusive or nosy manner in something that is not one's business or responsibility. I wish my neighbors would quit sticking their noses in where they're not wanted and just leave us alone! Don't stick your nose where it isn't wanted, Jim—your brother can manage well enough on his own.
stick (one's) nose in(to) (something)
To involve oneself in an intrusive or nosy manner into something that is not one's business or responsibility. I wish my neighbors would quit sticking their noses in and just leave us alone! Liam, don't stick your nose into your brother's affairs—he can manage well enough on his own.