I made a BOM and worked like crazy to get the darn thing sewn.When the top was finished, 2 blocks were turned. I sat down and proceeded to tear out the blocks and turn them. It took me forever. First, the quilt is something like 108 x 108... the blocks were each 12". It took ages to take out, turn them into the proper position, and then get them sewn back into the quilt top. I was satisfied with doing it (there was enough in the top to make in 'unperfect') but I wouldn't do it again. People that saw it before it was done said they didn't see any mistake. Granted these where not people that quilted, but I knew it was there and it would bug me forever. So... fix it if you can. Stitch by hand if you tear it out. Or applique something over it, if that is possible. But, I would leave it, if I had to do it over. It is lots of work.
Anita in Northfield, MN