He should pray to all kind of god and devil out there that the guy would agree to a settlement and drop the charge. Outside that, yeah pretty much plead guilty and ask for leniency. If what OP said about this being the first ever offense he got, leading guilty might help him get probation+ fine instead of jail time. Would still cost OP $3k-5k and medical cost for the guy + car damage though. But that's the best scenerio here.