if for some reason i have a block that is a few threads off, i don't trim down all the other blocks. i just make sure to line that block up with a good one, and sewing an exact 1/4 inch seam. the skinny one would have a tad less than 1/4 seam of course but as long as it's almost enough, it's fine.
by that i mean i line up three sides exactly and the skinny one doesn't fit to the raw edge of the really square one.