Is this normal/fine for a pci-e x16 slot?

I was in the middle of cleaning the dust build-up in my PC and when i took the gpu out carefully and got the gpu out. I noticed this

https://imgur.com/a/4YTvikF

This is the whole pci-e x16 slot area /w different angles.
https://imgur.com/a/1n79kss

Look at the red marked area. There’s some white like markings/patterns or something. im genuinely scared if i broke off something. Can this be cleaned using a brush or some sort.

And will it affect anything? Break something? Im dont know anything about the motherboard. FYI it isn’t bent the retention clip still works fine. or maybe im just paranoid.