Question

Thickening and discoloration of the nail of the index finger

Answer 1

Thickening and discoloration of the nail of the index finger
Onychomycosis (or nail fungus)

Answer 2

that would be a Fungal Nail Infections

Like bacteria, fungi thrive in warm, moist environments such as a nail. A fungal nail infection may start as a white or yellowish under the nail tip. When it moves deeper into the nail it can cause discoloration, nail thickening, crumbling edges that can cause pain, and a slight odor.