From your description it appears that the lung was collapsed partially by air leaking through the tear into the Pleural cavity. This is called a Tension Pneumothorax. Usually it causes the whole lung to collapse and if it continues leaking into the space may cause pressure on the heart and collapse the second lung. The usual way to relieve the pain is to put in a decompression needle into the upper part of the chest and this drains out the air. (a canuala)
Chest drains usually are put in to drain fluid from the pleural cavity as opposed to air but maybe they were getting both out that way.
It is a injury that can happen in divers but what I cant understand is the reason for it. Did they say what it was that caused it. As for the end of your diving career, well I wouldn’t right it off just yet. You need to go to a diving doctor to find out more really but I will make an enquiry as to whether it is a diving career ending incident.
Sorry to hear of your misfortune but don’t throw the towel in totally yet.