1. have unexpected negative repercussions/consequences
plans can blow up in your face
Something which 'blows up in your face' is an unexpected negative result of something you did (usually with good intention). For example, if you spent a long time saving money and kept it somewhere in your home, only to find out it was robbed you might say that saving the money 'blew up in your face'. This is a casual expression more suited to informal situations. Similar meaning to 'backfire'.