I did not know. "Didn't" is a contraction (shortening of) of the words "did not," which is the past tense form of the words "do not." Example: I arrived at the airport at 8:00 because I did not know (didn't know) the departure time was changed to 10:00. Hope that helps.^^

It just means that the person did not know what was needed to be done. (Or whatever the boy said he did not know to.)