Slightly thick/crumbly little toe nail.? there is no pain..? what can it be? what can be basic preventive/cure to get it back to normal?

Fungus or trauma: Pinky toes are subject to pressure from shoes. This can cause thickening and discoloration of nail. Also this can make nail more suceptible to fungus infection which can present the same way. See podiatrist for evaluation and diagnosis.

Possible fungus: This is most probably a fungus. Try filing it very short and otc antifungal cream to the area twice daily. If no relief after 2 months, than see your podiatrist.

Nail Fungus Infectio: Onychomycosis is a fungal infection of the nail. The nail darkens, can have a white dust on it's surface, or turn yellow in color. It is a very slow growing infection that often can evolve from an athlete's foot infection of the skin between the toes or the skin of the sole of the foot. There are topical medicines for this, but they have a poor record of success. Laser treatment is recommended.

Either fungus or : The nail could be thick from repetitive micro trauma. This is not uncommon in a 5th toe as it frequently is slightly turned and hammered and as a result the toenail hits against a closed shoe. The treatment would depend if it is fungal or thick from trauma either antifungal medication or a keratolytic exfoliator like urea creams or nonyx gel.