It's the very outer end of the jet that is at risk when you push something harder than the brass (or whatever the jet is made from) thru the hole.
Even tiny scratches / burs there, can alter the atomisation of the fuel - so it's easier and safer to use a plastic poker - or if you have brass jets and the muck is really tight - then a piece of copper fuse wire will suffice and can't scratch or distort the jet orifice.