deleted picture still appears in post

i deleted a picture from media library (permanent deletion). this picture was also inside a post both as a picture in the post and also as a featured image.

so when i deleted this picture from media library, it is no longer visible now as a featured image of the post, which i understand.

but the picture is still visible in the post itself, and in addition to that, when i click the picture while viewing the post, still the full size of the picture comes up. why?