Noting that rust really doesn't sleep, I'd clean it off with some paint-friendly rust remover (like Eastwood's Oxysolve) and/or treat it with a rust conveter. Then put a little touchup paint on it. A messier solution would be to spray a little rustproofing on it.
To really do it right you'd: run the bolt out, sand/etc. off the loose rust, treat with rust converter, prime with something like RustBullet or (my fave) Eastwood's Rust Encapsulator, paint, then run the bolt back in (having done the same thing to any rusted areas on the bolt, or maybe just replacing it).
