If we don't deal with it now, there will surely be trouble down the line.
Tips
usage
Almost always appears in fixed expressions: 后患无穷 hòuhuàn wúqióng ('endless future trouble') and 以绝后患 yǐ jué hòuhuàn ('to eliminate future trouble'). The latter is the standard reason given when finishing off an enemy in wuxia and historical fiction.