"Neměl jsi to říkat!"

Translation: You should not have said that!

[PierreMDL]

According all the sense I made of perfective / imperfective aspects throughout this course, I was expecting "Neměl jsi to říct"...

[svrsheque]

add to the sense you made. the speaker's disapproval of the action being described is often shown by the imperfective, even if the action is all done with and closed.

[igamenir]

That is correct, too.

[loudastepan]

Proc je zde předpřítomný cas pls? A je špatně: You should not said that?

[VladaFu]

https://www.helpforenglish.cz/article/2006062302-minula-modalni-slovesa