A bit of rust here and there is very common, and usually of no concern. The least concern would be for rust at the edges of the plates or on the rollers. Of greater concern would be significant rust in the center of the plates because it can weaken the chain.
But, chains are over built and only strong sprinters or those climbing steep hills need to worry about chain strength.
From the limited description in the post, I'd say, simply oil the chain to prevent more rust, and forget about it.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.