first of all, stop beating yourself up! Go have a glass of wine or a cup of tea and relax - almost everything is fixable and most of the time, only you will know there was a problem. The easiest is the fusible way. This depends on the size of the tear and if you can get in behind it. Then, if it is still noticeable, cover it. Either stitch the same fabric over the top, stitch a different fabric over it or do some sort of applique. Maybe the pattern will lend itself to a couple appliques in different areas of the quilt so it looks like a pattern. It is better to build on it than take it apart because that can cause a weakening. But, whatever you choose to do, it will simply make this quilt unique and your design!