Basically, I one day noticed that I had a small dent in my car that went all the way through the paint. I was told that if I don't put something on it, some kind of sealant, that it would rust which would be very bad. Since I can't afford to get it fixed yet, would finger nail polish work as a temporary sealant? Would there be another cheap fix that would at least not make things worse?

Thanks.

Yes. Nail polish will cover the dent and seal the area. There is no negative consequences to this practice.