If you can see light coming out of the silent switch, it will only be a matter of time and you will get dust on that corner of the screen. Others have had these problems and if near a store, I would get it replaced.
This issue happened with my iPhone 6S , I brought from Apple Online store , I live in Thailand
I got replacement for 2 time and had same problem , I think it normal issue because 6S had a 3D touch layer