In the old days, snowballs were made by cutting the corners off first, then sewing on the triangle
My 80 yr old aunt had a fit when she saw how I was making a set once, "you're wasting so much fabric! Your grandmother would be rolling in her grave if she saw this." She didn't like any of the "new fangled" way of cutting out quilts. Cardboard templates or templates made from milk jugs with sandpaper glued to the back, a pencil and a good sharp pair of scissors was all you needed. I wonder what she'd think of these new die cutters.
In this case I would:
1) cut down the main square to fit the triangles I have and then add borders to make the project big enough or
2) cut new small squares big enough then sew the too small triangles together to make some sort of border for this project or some other project or throw them out or
3) bag up the whole project and start over, congratulations you have your first UFO.