Use what you have. I made a small calculation error on a quilt I just started & had to seam the border. Honestly, it's no big deal & I think it looks kind of nice.
That said, I get how nerve-wracking it can be to make decisions outside of one's comfort zone. I got all panicky about how things would look on my little dresses quilt, but now it's all coming together nicely & I'm realizing that some of the things I got all worried about aren't even noticeable.