Swollen lymph node in pelvic area. its really tender and painful. hurts to walk. no other symptoms. what causes it? when will the pain go away?

Does "pelvic area" mean groin? If so, the usual cause is some sort of inflammation or infection in the leg on that side. It can be as minor as a hangnail. Cat scratch fever is a common cause in people who have contact with cats. Herpes and syphilis are possible if at risk for STD and/or if you also have a genital sore, pain, etc. See a doctor soon for diagnosis and possible antibiotic treatment.