The foot clinic I attend recommended coating the affected toe nail with Tea Tree Oil every day. Apparently you have to be patient as it takes about 3 months but it does do the trick. A small bottle costs about �6. I got mine from the clinic but have seen it for around the same price in several health food shops. I've read that the EEC want to add this to the list of banned products for some unknown reason so if you want to try it, buy some soon.
try to see a podiatrist,they will be able to advise you if it is a fungal infection,if it is ,it is usually secondary to a fungal infection elsewhere.(check heels etc ). so they would both need treatment.
hope this helps