Rust doesn't "soak in" to iron anymore than soup does. Whatever rust you see is on the surface. If you care about the appearance, get a knife not to use, as some people do with copper pans. Remove the rust with steel wool or (after wetting it with oil) with a razor-blade paint scraper. Then sharpen it. Cosmetic damage is the least that happens when a carbon steel knife is left wet. The first damage is to the edge. If you can't tell, it wasn't sharp to begin with.
Jerry
-- Engineering is the art of making what you want from things you can get.