The Dunning-Kruger effect describes people who don't know very much, but think they know a lot.
Dunning-Kruger also has a flip side where the people who are most capable consider themselves far less capable than they are (possibly because of this very effect where the more you know, the more aware you are of the things you don't know).
Oh you have met my Mother in Law. I did not know she had the nick name of Dunning-Kruger.