What should I do if the text message scolding my boss is accidentally sent to my boss's mobile phone?

Then go to work to see the boss's attitude. If he doesn't treat you differently, he can treat everything as nothing.

If he is angry and wants to fire you, there is nothing to be saved. If you want to go on, you can only beg him. Of course, it is likely that begging will not help. Because he usually makes a decision in advance.

If he just wants you to question and criticize you, then keep your head down and listen. It's best not to contradict you, even if you are justified. I don't think any boss will be generous enough to offend twice.