I would say get it fixed right away. I live in NY and the salt is terrible here. Once you get a rust spot it doesn't usually stop unless you get it taken care of.
Clean it, spray it, wax it and do it often. Also do not forget to clean the undercarriage as well. Also get the vehicle in a garage or park under and over hang if you can.
Sand it down and re-paint it right away. Try to find a rust protectant somewhere to apply before you paint. Something like that I'm afraid doesn't fix itself.
