I Think I Win

I think I win the award for stupidest quilting mistake ever!  I was working on this "leaders and enders" project a bit last night.  I've been working on this project for a couple years now as I piece it while I piece other things.  I really like the secondary pattern that is created with the off-white fabric and it is finally getting big enough that I was thinking that it might be time to put on a first boarder.  So I sewed a couple more rows onto the quilt and left it on my ironing board last night so that it would be out for me to work on today after my fitness class.

In the first picture you can see the sun shining on the quilt.  So when I was looking at the top today I noticed something really odd, confusing and frustrating.  Can you see it?  You might need to enlarge the picture to see it but it's there.

Hint:  look at the off-white background fabrics.

 Can you see it now?  I'm pointing at it.

Yep.  One of the off-white background squares is a completely different print in the same colour!!  How could I have:
a) got one square of this fabric into the stack?
b) not noticed this sooner?

This particular piece of fabric had to go through my sewing machine multiple times and I didn't notice it!  How could I have not noticed this?  I am completely confused.  Every other off-white is the same print except this one.

Now I am not really sure what to do.  Do I leave it and just try and pretend that it's not there?  Or, do I pull that square out and sew in a proper one?  If I am going to pull the block now would be the time to do it.  Once it's machine quilted it's not going anywhere.  I am starting to feel about done with this quilt so I think a lot of my frustration is coming from the realization that I have to do some really fussy work to re-work the center of the quilt. Yuck!

I just don't know what to do here.  Please leave a comment and give me your opinion!!!