What does hard dry chalky toenails mean just started in last 3 months or so?

Infection. There are various types of infections. Infections can be due to a fungus, bacterial or due to a virus. The treatment will depend on the type of infection and on what exactly is infected. Have it evaluated by a professional to get the appropriate treatment. By leaving it alone it may get worse.
Onychomycosis. Superficial white onychomycosis is a fungal infection which affects only the surface of the nail. Individuals with this form of infection will see white spots, usually in clusters, on the nail surface. In other words, it will be on the very top of the nail itself.