It's a social and cultural question. It depends on context. It depends on the level of formality. It depends on how serious the error it is and how easy it is to correct. It depends on whether you are trying to be kind, or whether you are annoyed or angry.A "Mistake" and "error" are good, neutral, factual words that can be used on all situations. You can use them, and let your tone of voice and body language take care of emotion. "Goof" is an informal word, and it is fairly soft. A "goof" is a minor mistake, of the kind we all make frequently. "There's a goof in this caption," or "You made a goof here." "Messed up" is stronger. It's a criticism. It's something that shouldn't have happened. And if something is "messed up," it need to be "cleaned up," i.e. corrected. "Screwed up" is stronger, and suggests that the speaker is angry. I don't think a foreign speaker should try to use taboo words, even if you hear them all the time in songs and on TV shows and YouTube. It takes a good understanding of a culture to know when it is safe to use them.

Mistake and error are both correct. You could say that "you messed up" as well, it is not great english, but we would say that in the US.

I think you can use "muddled".

Another possibility in this particular example is "a typo." "Typo" is short for "typographical error." It refers to a mistake that is made by accident, for example by typing the wrong keys on a keyboard, or typing them in the wrong order. A typo is an unintentional mistake. Like "goof," it suggests something that it not too important. Usually a typo is something short, such as writing "teh" instead of "the," or "Massachusett" instead of "Massachusetts." But I think your example qualifies. It was still a keying error, it's just that the key happened to be "paste." I had a friend who always liked to write "you made a tyop." That is, he was pretending to make a typographical error himself.