When piercings passing through cartilage become infected, it is possible for an infection to become trapped between layers of cartilage. When this happens, infection can spread very rapidly and literally destroy an ear within a period of a day or two creating ear collapse. Since the cartilage is the structural element of the ear, even after you've cleared the infection, permanent damage can easily be done.
A serious infection of this type should be immediately treated by a doctor. Again, this type of infection can spread and grow very quickly, so if this happens to you do not hesitate to visit an emergency room! See Cartilage Swelling for more information.