Can a toenail fungus last years in a single nail and it still be cured fully?

Maybe: First you need to confirm that you actually have a fungus. A piece of your nail can be sent to a dermatopathology lab, to confirm the diagnosis. If you do indeed have a fungus you can take a pill to see if it will work. If the nail is thick, laser is less likely to work.

Fungus: Oh ye of little laser faith. The answer is yes. See your podiatrist. When I use the laser in my office the nails is ground down to expose the fungus , then the fungus is killed with the laser.