get/have your fingers burned idiom informal (also burn your fingers)
（因错误决定而）吃亏，蒙受损失，（尤指）遭受金钱损失
to suffer unpleasant results of an action, especially loss of money, so you do not want to do the same thing again
She'd invested extensively in stocks and got her fingers burned when the market collapsed. 她在股市上大量投资，结果股市崩溃损失惨重。