I was thinking about joining a judo club near my house, but I was wondering what kind of injuries I have to expect by practising this martial art (I'm especially worried about my nose, my nasal septum is already deviated because when I was a kid I fell off a bike, and I don't want to make it worse).
This article summarizes it quite nicely with statistics for all injuries in Judo:
According to that research, there is a 7 in 1000 chance for boys and a 3 in 1000 chance for girls, based on historical statistics, of having a serious injury to the nose.
Caveat being that this is for young Judo competitors 17 years old or younger while they are actually competing at the national level. I would expect injury rates here to be much greater than that of a typical Judo school's injury rate. As such, consider this to be a maximum.
One interesting thing that pops out in that research and in others like it is that the injury rate in grappling arts like Judo is often much less than that of percussion arts like Taekwondo or Karate.
My own experience with Judo was quite positive. In the 2 years I trained in it, I didn't see a lot of injuries. I personally had nothing major during that time. Maybe the occasional headache from not being ready for a breakfall. Oh, and I recall stubbing my toe on the matts many times. It's not uncommon to hurt your toes that way. Fingers also can take some damage, because you're putting all your force into your grip. And backs can get messed up, usually because you're lifting wrong. That's why Judo has you repeat your throws thousands of times in practice before you start using them in randori (sparring).
Noses? Generally you're going to be thrown onto your back, not your front. Almost no throws land you on your face, but it is possible if it happens by accident. And it's possible your opponent's knee, elbow, shoulder, or head butts into your nose at various times during your training. That should be rare, and only by accident. And there are no strikes to worry about, so that's good.
There are some head protectors that have built-in nose protection. But I've never seen anyone in Judo wearing them. Still, I doubt any Judo teacher would tell you not to wear one if you wanted. If you do get one, try the ones that have a cage enclosure around the front of the face instead of the ones that have padding. Something like this: