Thank you everyone for your commisseration and advice on how to fix the block. Joan had suggested, and I was already thinking in my mind, that I should do an organic curve-shape over the top. I got a scrap of the backing and matched the pattern to the backing piece, pinned, and then basted in a curve. I did consider carefully if I should make it larger, or keep it smaller. In the end, I went with smaller. Here is the finished block--trimmed down the correct size including the seam allowances.
Here it is with the seam allowance covered.
Have any of you ever "made a mistake" or otherwise pieced something not quite right, but could never find it in the finished quilt to fix? I once was piecing a quilt and had exactly the right amount of fabric for the backing. I had cut the stip and was subcutting the units and did what many of us do, and didn't line up the ruler just right and cut one a bit too long, and the other was too short. So I was short 4 to 6 (I can't remeber how many thicknesses I was cutting) pieces. I went to my stash and found something "similar." I used it and when the quilt was done, I had a really difficult time finding those pieces in the quilt.
Thanks also for the well-wishes. The procedure that I had surgery for was something most people can get done in the office, but I guess not me. We know because they tried twice! It is over now and I'm pretty much back to normal. I am having company, though, our daughter is visiting! It was her birthday yesterday and it was the first we've spent together since she turned 18. She is now at an age where I no longer share it! I have had no problem with my own birthdays, but boy, when my child becomes a certain age--well, that makes me feel a bit old.