I was a nail tech for 15 years. You have nail fungus. You can get an antifungal gel from a professional nail tech called Dr. G's. It's about $15, but it's the best. It's a very effective treatment if used correctly. The biggest mistake people make when trying to treat the fungus is clipping the nail too far back and/or digging under the nail with an orangewood stick or other device. This just lifts the nail from the bed encouraging new fungal growth. For correct application of the antifungal gel: Without lifting the nail, apply the gel by squeezing a bead along the tip of the underside of the nail and let it spread on it's own. It will start to work immediately, but continue applying daily until you begin seeing normal nail growth. The existing fungus will not go away, but it will stop growing. Continue clipping the nail, careful not to clip too much, and filing to smooth it as it grows out. It will take 4-6 weeks for the nail to
replace itself.
If the fungus does not go away with Dr. G's, you need to see a physician and possibly undergo a more invasive treatment such as Lamisil. Try the least invasive treatment first.
If you need more info, message me. HTH