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.