Since I do screen replacements for iPhones on a daily basis especially iPhone 5 and 6 series what I do is just remove the grey foam sponge thing that is stuck onto the camera around the circle.
That way when the phone is put back together you don't see it obviously being not perfectly in the middle.
This does not affect the functionality of the camera though.
Do make sure to clean the front camera if the previous screen had cracked glass missing which would expose the front camera lens to dust.
I would just live with it. Really like 99.9% of my clients that come in to replace their screen do not care if it's not perfectly aligned in the middle.
I suppose you could use like B7000 liquid glue to get it in place but the problem is getting it aligned first and it takes some time for it to set well.