NOT TO SLEEP A WINK

Sally notices that Peter is not feeling well, so she decides to strike up a conversation with him:

SALLY: Hey Peter, what's wrong with you?

PETER: I had a terrible stomachache last night and I didn't sleep a wink.

SALLY: Oh, dear! Why don't you see a doctor?

PETER: I've taken some medicine already. If I don't feel better, I will.

SALLY: Ok, then.

Peter DIDN'T SLEEP A WINK last night, so it means that he didn't sleep at all.