It should be pretty easy to rub the grout off the plastic skimmer mouth. I don't think it looks all that great, but I wouldn't make a big deal out of it. If you hadn't been inspecting every inch of the pool because it's new, you never would have noticed it. I don't spend all that much time looking in my skimmer mouth...it's kind of scary.
If that's the biggest issue you have, consider yourself very lucky!