Default [HELP] MD5 problem with Galaxy s4

I messed up real bad by the looks of things. I was trying to install the Cyanogenmod update, but that went wrong and my phone got stuck on the Galaxy s4 screen during the load up. I got it into recovery mode, but it tells me there's an md5 file mismatch. I can't even plug it into my computer via usb, for some reason, does anyone know what I can do?