I'm not sure there is a good solution to this. I guess it all depends on how many blocks are too small. If it's just a couple & you have or can get more fabric, I'd recommend remaking those blocks so they're the right size. If it's a bunch of them & you can't/won't remaking those blocks, as far as I see it, you have 4 options:
1) Check your seams. You need to measure from the
front of the fabric, not the back. Make sure that your pieces are finishing at the proper size. Depending on how many seams you have, the difference between sewing a 1/4" and a scant 1/4 can produce up to a 1/2" difference in a block's size. If that's your culprit, unsew the problem blocks & carefully resew with a scant 1/4" seam. You might try marking the seam allowance & then sewing just to the right of the marked line.
2) Square everything up & lose the points. You'd be amazed how often this happens. It's really not the end of the world. Take it as a learning experience & move on to the next quilt.
3) Fuse or sew more fabric to your blocks to extend them. Depending on the block's fabric, color, # of seams, you could either fuse the whole thing to a larger piece of fabric, or just fuse/sew 1/2" of fabric around the edges. For this technique, you'll want to sew with a generous 1/4" seam (instead of the standard "scant 1/4") so the added fabric is entirely caught up in the seam. It will mean you lose just 1/16" of your points, but will be much less noticeable than losing 1/4" off it.
4) Unsew everything & re-cut based on a smaller size, to scale. Your quilt will finish a bit smaller, but you can always add on an extra border to get to a pre-determined size. It's the most work, but will yield the nicest results if you can't get material to remake the blocks that ended up too small.
Good luck! We've all been there & whatever you decide is the solution for you will be just beautiful. Those imperfections in the quilt will become part of it's story and will add to its richness and beauty. How we handle those challenges is a lesson for the generations as we explain over time to our children & their children about why the blocks have no points. Every quilt carries a story; perhaps this is meant to be part of the story of this quilt.
