Sometimes when I make my blocks they aren't all the same finished size, so I'll rip out the seams and sew it back together. I never had any problems doing this making clothes, but apparently it's a no-no in quilting. I have gotten quite a few of these little holes over the course of my quilting career. This particular hole is right on the line where the old seam was before I undid it and re-stitched it.
What am I doing wrong?! And how do I fix it?