Answer: Onychomycosis
Step-by-step explanation:
The onychomycosis is a fungal infection seen in the human nails. It is also known as tinea unguium. The symptoms associated with this infection include the whitening, yellowing and another kind of discoloration of the nail. The nail thickening and separation of the nail from the nail bed are also the features of this infection. The toenails, as well as fingernails, can be infected.
Based on the above explanation, this can be said that Nick is suffering from onychomycosis.