What does it mean when your gums in the back are swollen?

Means bad news !: If the gums are swollen, and also bleeding and tender.. It can mean u are experiencing some level of periodontal disease. But if it is swollen on one tooth area, it can be also due to an infected root, fracture of a tooth, ot reinfection of an old root canal. See your dentist and with proper exam and radiographs he can tell you what is going on.

Pericoronitis: Which is the inflammation of the gums around the wisdom teeth, mostly impacted ones, but not necessarily. It is the most likely diagnosis but not the only one.