Is a nose job allowed Hallachicly? Not all cosmetic surgeries, but rhinoplasty in particular, as I heard that rhinoplasty is allowed because we see by a Kohen that having an abnormally long nose is a disqualification for serving in the Beis Hamikdash. (A source for that line of reasoning would be highly appreciated.)
See this comprehensive survey at Aish, about plastic surgery in general. It mentions this kohen reason, in the name of Rabbi Menashe Klein, in his Mishneh Halachos, and (IIUC) Rav Shlomo Zalman Aurbach. But others permit for very different reasons:
Then, a bit later:
He ruled in favor of allowing her to do this. In part,
A bit later,
There is also a position that it is OK except for the sakanah involved in it:
A halachic position against plastic surgery, including hashkafically:
And finally, Rav Shlomo Zalman Aurbach:
For precise sources, follow the link to the article and look at the footnotes.
Funny that today we all think about the need for "nose jobs" and cosmetic surgery for noses that are too long; in theory, a nose too short is a disqualification for a Cohen too! For a less vain example, let's talk about the case of the crooked nose (also on the list).
Rabbi Moshe Feinstein had allowed rhinoplasty for young woman who felt that her nose was seriously hurting her efforts to find a suitor. It has to do with when one is allowed to have injury caused to one's self (not to mention risk) for valid reasons.
(From here on out is my own reasoning, not Rabbi Feinstein's.)
The problem here becomes -- as America today is beginning to realize -- that we can get these very distorted senses of what's "normal" and not (e.g. based on the photoshopped faces we see on magazine covers), and before you know it, everyone "needs" a nose job. (What about this case of the newlywed groom who storms into the rabbi's office, furious that he doesn't like the look of his bride's private parts. Is the correct response she may have cosmetic surgery for the sake of their marriage, or is it slap this kid upside the head, yes this is what a real human being looks like so get over it). This is more of a philosophical question.
Note that Judaism believes in the use of science and technology to cure diseases. So we'd be inclined to say that if someone is actually disfigured, by all means use plastic surgery to "fix" them back to "normal." If someone was born with a perfectly fine, healthy nose that isn't quite the latest style these days, well then better to have some faith and be satisfied with one's lot.
One line that could be proposed is, as mentioned above, based on the list of disqualifying blemishes for a Kohen. If a woman was hiding one of these blemishes and she met a man who married her and thus agreed to paying her Ketubah, upon discovery of the blemish he could void his monetary offer. So it could be suggested that anything on the list (or equally severe) is something that medicine can fix (if we feel it needs fixing! If she was born without eyebrows but both he and she like the look, that's fine too). To try and fix anything else would be hubris.
As such I'd wonder if, in instances where plastic surgery is indicated, the goal should be an "averagely-proportioned" nose, not a "Hollywood photoshop nose." It's amazing how all the people on these plastic-surgery makeover shows wind up looking alike after the procedures.
Just to add to the many valid opinions already brought down, Hacham Ovadia Yosef (Yabia Omer C"M 8:12) permits all forms of plastic surgery for both married and unmarried women and men, as long as they do it by a professional to minimize the risk.
Here is the relevant conclusion: