Among the physical defects which disqualify an animal for use as a sacrifice are a number of defects that appear on the animal’s nose. These are listed by the Mishna in Masekhet Bekhorot (39a), and the Gemara adds the case of “nikevu chotemeihen zeh le-tokh zeh” – a puncture in the flesh between the two nostrils. The Gemara establishes that if the puncture is in the exterior part of the nose, such that it is visible, then this condition constitutes a disqualifying mum (defect). If, however, the puncture is deeper inside the nose, then it does not disqualify the animal.
The Rambam, in Hilkhot Bi’at Mikdash (7:6), applies the various disqualifying defects in the nose to the case of a kohen. Just as an animal with these defects is disqualified as a sacrifice, a kohen with these defects may not perform the service in the Beit Ha-mikdash. Curiously, however, as Rav Yosef Karo observes in his Kesef Mishneh, the Rambam omits the case of “nikevu chotemeihen zeh le-tokh zeh.” He applies to the kohen the other disqualifying nose blemishes, but not the case of a puncture from one nostril to the next. Apparently, the Rambam felt that this disqualification applies only to animals, but not to kohanim. The Kesef Mishneh leaves it as an open question why this condition disqualifies an animal but not a kohen.
A number of Acharonim, including Mahari Kurkus and the Chasdei David commentary to the Tosefta (Bekhorot 4:2), suggest that the Rambam distinguished between animals and kohanim in this regard because it was customary to wear nose rings, which involved puncturing the flesh between the nostrils. As such a puncture was considered standard, and not something unusual, it does not qualify as a mum, and thus although it would render an animal unfit as a sacrifice, it does not render a kohen unfit for performing the service.
Rav Yitzchak Zilberstein, in Chashukei Chemed (Bekhorot, pp. 434-435), addresses the question as to the status of modern-day nose piercings, which some people make in the exterior flesh of the nostril. The Rambam writes explicitly that such a puncture constitutes a mum and disqualifies a kohen, but in light of what we have seen, one might argue that once this kind of piercing has become common, it no longer constitutes a disqualifying defect. The practical contemporary relevance of this question, as Rav Zilberstein notes, would relate to the eligibility of a person with a pierced nostril to lead the services in the synagogue. The Mishna Berura (53:13) cites the ruling of the Magen Avraham that it is preferable not to allow a person with a visible physical defect to lead the services, unless there is nobody equally as or more qualified. According to this view, the question arises as to whether somebody with a pierced nose may lead the services, in light of the fact that such punctures are somewhat common and thus not regarded as a defect. Rav Zilberstein concludes that it seems more likely that the halakhic definition of “mum” depends upon the norms at the time the Torah was given, and not on the norms of any given society or time period. Therefore, in his view, a pierced nostril would constitute a mum even nowadays.
It should be noted, however, that the Mishna Berura – before citing the aforementioned ruling of the Magen Avraham – takes a different position. He writes that a physical defect does not disqualify a person from serving as the shaliach tzibur (leader of the services), adding that to the contrary, as David says in Tehillim (51:19), “A broken, depressed heart is not rejected by God.” People with physical defects who feel ashamed and disheartened by their condition are especially beloved to the Almighty, and thus have an advantage over others in terms of eligibility to lead the services.