In that area of the board I'd check your audio. Try all the jacks in both the front and rear panel audio panels, including the optical or digital output jack if it has one. Of course, change volume and listen for distortion. If you can't really check some of them and/or never use them anyway so don't really care...then if working all right otherwise I would just continue using it.
As far as long term: if you're really, really worried AND you live in a high humidity area you might cover the scratches with some clear fingernail polish. Just to seal the board so any moisture that might condense on it there doesn't easily get in.