TT #215 · Parshas Tazria · Aliyah 5 · Passuk 37
English: If the netek remains unchanged and black hair has grown in it, the netek is healed; he is clean, and the priest shall pronounce him clean.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:37
Torah Temimah cites Sifra (Toras Kohanim) for excluding a nested netek from the definition of a healed netek.
Sifra — Vayikra 13, Midrash Sefer
English: 'The netek is healed' excludes a case where another netek has formed within it.
Textual derivation
A nested netek is not treated as a healed lesion.