HELP! Any way to remove a scuff from decal

Boy that's tough, that vinyl isn't going to take much scrubbing.

Try (AT YOUR OWN RISK), a very tiny dab of toothpaste on a soft cloth with light to moderate pressure. I use toothpaste to clean tiny scratches off my glasses, so it "might" work, I dunno. Just don't go into full scrub mode, lol.

Do you have a vinyl bumper sticker or something of the sort to experiment on?

If it does, then you could follow up with a small dab of polish.