he who rides a tiger is afraid to dismount—unable to extricate oneself from a difficult situation
骑虎难下
ride a tiger and find it hard to dismount—have no way to back down
骑虎难下势成骑虎（shì chénɡ qí hǔ）qí hǔ nán xià
骑着老虎难以下来。比喻遇到困难，但是为形势所迫，想不干又会造成重大损失，故不得不硬着头皮干下去。have no way to back down, be in for it, have a wolf by the ears, up a gumtree, up the people, up the creek, in chancery