TT #138 · Parshas Tazria · Aliyah 2 · Passuk 14
English: But as soon as raw flesh appears on them, they shall be impure.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:14
Torah Temimah cites Sifra (Toras Kohanim) for excluding lesions associated with the head, beard, boils, and burns.
Sifra — Vayikra 13, Midrash Sefer
English: “On the day it appears” excludes lesions on the head and beard and those arising in a boil, burn, or inflamed area.
Textual derivation
The rule excludes lesions on the head or beard and lesions associated with active boils or burns.