Good eye!
Here is the original photo used for the artwork:
https://portal-ccc.s3.amazonaws.com/...87/125r836.jpg
It looks like a pocket on the sweater to me. The color should match the rest of the trim on the sweater if that's the case. There is a shadow from the hand too which helps to make that area extra messy. I think they may have goofed it up with the color. I think the button up around the neck was a mistake as well. They changed the color of the hat too which it isn't uncommon for a card to vary from the photo slightly.