If you are just starting out in boxing, make sure you learn how to guard your body and head effectively and can punch and block from your guard position. I would not make a good boxer but because of the Tae Kwon Do, I can do kickboxing. The kicks come easy. My hands are still not the best but I did not start kickboxing in the conventional and nice way. I didn't have any training whatsoever before my first match. I was just thrown into the ring with a guy who had been training for six years in muay thai thai boxing. Do NOT learn that way. You learn fast but you stay in that mentality and it is hard to get out of it. As for that match, I got third place out of ten trained men. I was the only female in the entire event.
Everybody's injuries can vary
I am 60 and have been boxing since my teens. I boxed in the Golden Gloves from the age of 21-25, from 1972 through 1976, and later in my late 30s and 40s as a masters "white collar boxer." I have rotator cuff issues which may or may not be a result of boxing and sparring, and mild arthritis in both hands, which my rheumatologist says again may or may not be a result of boxing. As an amateur, I fought a total of maybe 90 rounds, with headguards as amasters boxer though not in the Golden Gloves, when they had not yet become mandatory. It is very unlikely that the average amateur will sustain long term affects to the brain, such as the Parkinsons disease Ali has, or the dementia pugilistica which affected the Quarry brothers. On the whole boxing is a fairly safe sport with fewer injuries than football or even hockey, so I think you need not expect much in the way of longterm damage.