Typically a rust spot doesn't develop in a week on a new gun. Did you try and clean it off. Usually the finish has to be compromised in some manner before rust will take hold. Unless there was a nick in the finish, or a bubble some how under the finish I can't see how it would have rust already.

Gun socks will work fine if the gun is clean and has a coating of oil on it. If you're in a moist environment or the gun isn't cleaned before putting away I would avoid a gun sock. The oils from your hand are more likely to rust the gun over time than anything else.