Like some of the others said an eighth of an inch is probably ok. I have been known to go over a seam with smaller stitches to make sure it wont unravel when washed and all my quilts are washed after I finish them and so far those seams are fine. If it isnt going to mess up your block I would take it out and redo but when it is near impossible to do that I do the tiny stitches over those seams.