It's Fungus growth on nail..it will go with medicine.. for detailed prescription do direct online consultation

One of the most common causes of yellow nails is a fungal infection. As the infection worsens, the nail bed may retract, and nails may thicken and crumble. In rare cases, yellow nails can indicate a more serious condition such as severe thyroid disease, lung disease, diabetes or psoriasis. Consult a Dermatologist fort he same to know the underlying cause of this discolouration and prevent further spread.