stick (one's) oar in(to) (something)
1. To offer or express one's opinion (on some matter), even though it was not asked for or desired. Primarily heard in UK. I don't know why you feel you have to stick your oar into every dispute Terry and I are having. The members of the board are perfectly capable of arriving at a decision of their own accord, so I'll thank you for not sticking your oar in, Tom.
2. To involve oneself in an intrusive or nosy manner into something that is not one's business or responsibility. Primarily heard in UK. I wish my neighbors would quit sticking their oars in and just leave us alone! Liam, don't stick your oar into your brother's affairs—he can manage well enough on his own.