Honestly I don't think about it. I live by an old rule. If you have to tell someone you're smart then you're not.
So as a parallel if you have to tell someone you're an expert then you're not. Just do your shit, if you're good people will listen to you or ask your advice. That's your answer to if you're an expert.
"Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t*rd by the clean end"