Holy crap bro! This is turning into a bigger and bigger "woops" as the days progress. If I were you I'd be loosing my mind by now.
But I'll answer your question with another question: how deep (roughly) is the groove? Is it around 1mm or less? Pics would help us juge this a little better. Hopefully that impact didn't result in a fractured piston sleeve or even worse - a damaged crank journal.
I don't remember your setup quite that well, did you use forged or cast pistons?