You likely have a nail fungal infection if one or more of your nails is:
Thickened
Dull — with no lustre or shine
Brittle, crumbly or ragged
Nail fungal infections can get worse
Dark colour — the result of debris accumulated under your nail
Distorted in shape
Separated from the nail bed — a condition known as “onycholysis,” which may cause pain in your toes or fingertips, and be accompanied by a slightly foul odour.