It looks like surface rust, and is probably not harmful structurally - yet. If it was my bike, I would wash that whole inside area that you have pictured, perhaps just with rags and cleaning solution, and then hit the clamp with some method of rust removal. Not necessarily chemical means, but some scrubbing action, and maybe a light application of a rust remover.
My N300 needed a whole new head bearing at 12k miles, street ridden only. That was when I bought it used. Who knows what happened to it before then. I have had zero issues with the "All Balls" head bearing upgrade my shop put in, and I am at 50k miles now, street riding and a good amount of track. Given the bikes mileage, I would replace it soon anyhow if it wasn't kept up.
Plus, yeah, the head bearings need some love from time to time. Unless you have bearing press tools and experience jacking the front end of the bike up, have a reputable shop take care of either a replacement or just a lubrication. I think most shops wouldn't perform a "lubrication" job though, they would say if they are that deep in it, to just replace the bearing.
If you notice any steering oddities that are not remedied by a retorque of the head nut and clamp bolt, then have it serviced. But if I was you, I'd clean that whole area up by hand just for peace of mind.
-Mike