Sorry for telling you terrible things.
Sorry for saying terrible things.
?
偉そうな言い草
self-important 「speech [words]
偉そうなことを言う
talk big.
偉そうな口をきくな。
Don't talk so big. | Don't 「be a snob [brag].
(新和英大辞典)
My bad. I should have checked 偉そう, not 偉い. :-)
Thanks, Tommy!