Located all over the body, they are found in armpit, groin and back ear areas. The swelling of small bumps behind your ears could be as a result of swollen lymph nodes. You can feel these swell up when you have common infections such as tonsillitis, mono, colds and flu. These could remain swollen for a number of days or even weeks. Note: rarely do cancers and tumors cause lymph node swellings.