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Your officially screwed
Nah, just kidding. It can be done but probably not the way you would like too.
Since its from a sharpening stone, the scratches are probably a little much for just buffing out. You've basically gouged out a
TINY little furrow in the steel. To get rid of it you have to remove enough material to flatten out the surface again. You could do it with a buffing wheel and rouge with the dremel but it wouldn't match the finish on the rest of the knife, unless its mirror polished. And then it would probably have a streaked look.
Instead, you'll probably get better results putting a hand rubbed finish on the blade. Since its minor scratches I'd start out with a fine grit of wet dry paper, like 320 and see how things look making passes in the same direction as the original finish on the knife. Concentrate mainly on the scratched spots.
Don't sand back and forth, it will leave circular scratches. Make straight passes starting in the same spot every time and going all the way from edge to edge or bolster to tip depending on what direction the finish runs in.
When you have the scratches out, switch to a finer grit. Go as fine as you want, or until you match the original finish.
Then resharpen the knife

Its a vicious cycle
Chances are if your friend asked you to sharpen it, they plan on using it and won't be all that upset about a few scratches. Somethings you just have to learn to live with. It just can't be avoided with a knife you want to use.
I'm just assuming that the scratches are pretty deep. If they are really minor, there is a chance you could buff them out fairly easily wityh the right stuff but I don't know exactly what that would be.