I agree about just enjoying it! We all have plenty of stories to share about our first quilt & this will be yours. I'm assuming you hand quilted it (I can't even begin to imagine doing a King-sized quilt FMQ on a DSM for a beginner). If that's the case, you're in very good company. Many antique quilts were made with whatever batting-type material was around -- sometimes that was just a layer of flannel -- and they were nearly flat. Over time, as the quilt became more worn, or if the quilter had managed to gather enough flour sacks to piece together a new top/backing, she would layer them on top/bottom of her existing quilt -- sometimes with a bit of extra "batting" -- and would start again. There have been many people who have taken a vintage quilt either to be repaired or appraised only to find out that it was multiple quilts in one. Maybe at some point this quilt will become that -- your original quilt will be encapsulated in something new & thereby preserved for generations to come as a hidden treasure. In the meantime, I hope you can still find ways to enjoy it.
If it's a low-loft cotton, it will crinkle when laundered & the quilting will likely become more defined. Unfortunately, that doesn't happen with low-loft poly. But there are many quilters out there who choose low-loft batts specifically so it stays very flat & the piecing is the star of the show. Perhaps you'll find a silver lining yet in your "mistake".