24 year old male. horizontal ridging in toenails. nail feels a bit rough. mainly in big toe and toe next to big toe. fingernails not affected. normal?

Probably Normal: Horizontal ridges in the nails may be associated with trauma, acute severe illness, malnutrition or metabolic condition, chemotherapy and results from any interruption in the growth of the nail plate. Given the isolated nature of your nail ridges, local trauma to the great and second toe are most likely the cause of these findings in an otherwise healthy person.

Usually: They're called Beau's lines. May occur from temporary cessation in toe nail growth. Eg trauma. In cases of malnutrition they can also be found. But if you're otherwise healthy, they are normal.