Excuse Me, May I Borrow Your Light?

借光 [jièguāng] means "excuse me." But the literal translation is "to borrow light" in Chinese.
I'm paraphrasing an old story here:

Imagine two houses very close together. In each house lives a young girl. Julia lives in the house on the right. Karen lives in the house on the left. One day Karen's parents became ill and can no longer work day to day as shoemakers. Karen wants to help her parents so she works through the night to get things done. However her family cannot afford to have the lights on, so she works in the dark as much as she can. One day she realizes she can use the light that is coming through her neighbor's window to work. Karen does this till Julia realizes what is happening and shuts off that light. Karen goes to Julia and says "Excuse me, may I borrow your light? It is insignificant to you to have that light on, but it means the world to me because I can help my family."

This phrase may be more common: 對不起 (T)/ 对不起 (S)/[duìbuqǐ].
This also means excuse me, but has a underlying meaning. When you said this you are also implying, I have done you wrong - I am beneath you, you are above me in status. Nuances! I now it is hard enough to remember the vocabulary and meaning.