What did I do wrong?

I am soooo frustrated. I'm making a quilt. Square in a square. Inner
border. Outer border with mitered corners. I just finished putting the
outside border on and laid it flat on the carpeting. The square in a square
part is "bunchy"... looks like there's excess there and doesn't lay
perfectly flat. It's like the inner border is too small. I measured across
the middle when measuring for the inner border. I thought it might be the
mitered corners. I took those out - no difference. Could I have stretched
the middle? How? When ironing?

I'm not going to be quilting this project. I'm passing it off to another
mom to quilt and then we're donating it. I'm embarrassed to give it to her.

Is there any way I can correct this at this point?

--
Gina in IL
http://community.webshots.com/user/dgelias