Rust = inevitable when you've got iron and water and oxygen together. People are very skittish about a bit of rust. Track nuts chew up dropouts, so the paint always comes off. If it's a steel dropout, and you've not sprung for the bling stainless or chrome option, then the exposed metal will rust.

If it ain't eating into your metal, it's fine. When you clean the bike - whenever that is, probably about March now if you're like me (!) - just rub the clean, dry rust with an oily rag. You can use Kurust or a similar product if you like, but I stick with oil and rubbing. It's universally good..