Finishing metal that you had to file?

This has always been a mystery to me. I recently got a new CZ-52 9mm barrel that required some fitting on the barrel and the roller cam to work in my gun. Nothing major - about half an hour with a file or so.

The thing is, I now have some parts of the metal that were originally blued that I had to file that have had the finish removed.

They're internal so it's not a visual issue, but for rust prevention, etc, should I worry about applying a finish (cold blue, etc) or just leave it in the white and oil it?

Thanks.

Thanks for the advice guys. The area that I had to attend to is completey hidden when the gun is reassembled so I guess I'll just oil it and call it a day.

FYI to anyone else looking at one of these Federal Arms replacement barrels that may be floating around: the chamber on mine is VERY tight. Factory stuff seems to fit ok, but for my reloads I have some rounds that actually fit a Lyman case gauge that won't fit this barrel.