If I block somebody on iPhone does it delete messages off their phone?

I sent a message to the wrong person, now they are going to show everybody, if I block them on iPhone/iMessage/FaceTime, does it delete the messages off of their phone?

No. It doesn't even delete it off yours.

No nothing you do on your phone will affect anything on another phone.

All blocking does is prevent the blocked person from contacting you on your phone after they are blocked.

What's done is done it can't be changed.