ᴱQ. nyelet “nail (of the finger)” appeared in the English-Qenya Dictionary of the 1920s with a plural form nyeleksi (PE15/75). It was probably related to ᴱQ. nyelekka “onyx” from the same document (PE15/76).

Neo-Quenya: I’d retain the word ᴺQ. nyelet “finger nail” for purposes of Neo-Quenya derived from a Neo-Root ᴺ√NYELEK, but I would assume that its stem form is nyelec- because (a) I think the plural nyeleksi may be the result of Early Qenya phonetic changes like how [ti] became [tsi] and (b) a stem form ending in ks- would become a final s in later Quenya phonology (PE19/104).