I don't think there is anything you can do. Sending it to Nintendo is probably your best option.
For most of your options with a black screen, read this-
OH SH*T: Black Screen of WII!!!
It is amazing how easy it is to accidentally uninstall an ios. Kinda like accidentally sleeping with someone's wife, I know it happens, you trip and fall, and you know... It was a accident, I didn't mean to.