Depending on how bad it is, you can buy a good anti-fungal cream to treat it and most all do the job. They are OTC products like Lamisil or Tinactin. But if it's bad, you should see your Doctor as there are some prescription strength creams also.
What are some remedies for toenail fungus?
I have heard that Listerine and lemon juice both work quite well due to their antiseptic natures.
I agree with all the answers and I'll add one more....Vicks vapor rub!