How do I wash fabric that is 73% nylon and 23% Nailon (is spandex)?

I have a hot pink spandex type running jacket. It does not give washing insructions. Well, I got a little ink stain on the cuff from a pen, so I washed it out with hot water, nothing else. Since I didn't need to wash the entire jacket, I washed just the sleeve. Well, now there is a water mark dried onto the sleeve where the cut off point was (from where I washed it to the dry part). It's dried, but I have this water stain. I don't know how to get this out and how to prevent it from happening. Now I'm afraid to wash the entire thing for fear of getting water marks everywhere!