That's one of those times where you wish real life had an "undo" button! Been there, done that!
Mine wasn't quilted yet so I eased the block out and sewed a new one in place - it was just one block in from the edge so I was able to partially undo a couple seams, get it out, and sew the new one in and put it all back together by machine. I avoid hand-sewing when I can!