TT #217 · 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 the need for a formal priestly declaration of purity.
Sifra — Vayikra 13, Midrash Sefer
English: If the verse said only “he is pure,” one might think he could leave without a formal declaration. The words “the priest shall pronounce him pure” require the priest’s declaration.
Textual derivation
Even when the signs indicate healing, the person is not formally released from the netek’s status until the priest declares him pure.