A proverb meaning that a pressing need may force you to sacrifice something else; you must accept a smaller loss to deal with a greater problem (you can't make an omelet without breaking eggs).
会社が倒産しそうだから、給料を減らすことになった。背に腹は替えられぬ。
The company was about to go bankrupt, so wages had to be cut. You have to accept the lesser of two evils.
急な出費で貯金を下ろした。背に腹は替えられぬというものだ。
I withdrew my savings because of an emergency expense. You have to make sacrifices when necessary.
病気の治療のために旅行をキャンセルした。背に腹は替えられぬ。
I canceled the trip to pay for medical treatment. Necessity prevailed.