mustn´t in the past tense

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hello!

What is the most precise or correct expression of mustn´t in the past tense?

I mustn´t go to work, the doctor said.

I mean from the semantic point of view, because there are several possibilities as wasn´t allowed to, couldn´t, etc. but which one is the most exact?

Thanks

2

“I wasn’t allowed to” (or similar) works if “I mustn’t” means “I’m not allowed to” (i.e. someone is forbidding it). However, “I mustn’t” more often suggests a self-imposed restriction (“I mustn’t eat any more of those chocolates!”), in which case I can think of no past tense form without becoming very verbose. Although “I shouldn’t…” is close in the present tense, “I shouldn’t have…” has a different nuance, suggesting that actually you did. I can’t think of any sense of “I mustn’t” for which “I couldn’t” is a reasonable past tense. Sorry, you might be able to use “couldn’t” in the sense of “wasn’t allowed to”; I was thinking of the sense “wasn’t able to”. (I knew I shouldn’t have embarked on this question!)

By the way, you are using the wrong character for the apostrophe. You seem to be using an acute accent (´). See if you can find on your keyboard the character ’ or ’.