Just scratched the right-middle side of the bottom (GLK). Something got loosened (one screw)

do you guys think there is big issue, or I have to go to dealer to check?

Thanks

First off, Sorry that you had a run in with what was obviously a rather large and hard object. I hope you know that you will most likely be hounded until you do tell how this happened. Hint! Hint!

At first glance it does look more cosmetic than structural. Of course the best answer for determining if this is just cosmetic or more serious will be from an MB dealer or highly qualified body shop.

Good luck and I hope that it's just a scratch.

You are fine. That is just a large piece of plastic protecting the bottom. You can always buy another or just cover the holes with duct tape.