Personally, as a new quilter, I would probably suggest easing them in as Barb suggested, and chalk it up to a learning experience. Oversizing the HST, then trimming them to size is a common practice. Another thing would be to make all your HSTs, (make a few extra). Find very smallest & discard, then cut the rest down to the smallest ones left THEN cut your squares to match. This obviously will only work if the quilt top is made from squares & hsts.