How should I cure my toenail fungus?

It first appeared when I got a job and was working on my feet a lot. I don't know what exactly caused it. At first it was discolored (dark colors especially such as black, brown, a reddish/purplish color). Now it's a yellowish color and the nails are thicker than they should be. I want something to cure it, and I'm hoping there's something that has no side effects and very little to no pain.