Rust is not a serious problem on a blade. It happens on low end knives to very expensive high end knives and is mostly a maintenance issue.
It can be removed easily with metal polish. Flitz is AMAZING, and Brasso works okay on rust (but much better on brass tarnish). But if you don't have that, toothpaste will do a surprisingly good job (better than soap and water, but worse than Flitz). Just put a dab of your choice of paste on a rag or paper towel and rub in a circular motion. Should take just a few rubs to clean off.