What could cause the swelling of lymph nodes in groin?

Inflammation / tumor: Inflammatory swelling often due to skin infection or cellulitis of lower limbs or genitalia or cat scratctch disease, can be related to stds such as chlamydia, gonrrhea etc..Also viral coditions eg mononucleosis & side effects of certain drugs. Various malignancies eg: leukemia, lymphoma or genital cancer. Should be checked out if swelling present or persists for more than about 3 weeks.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.

See your doctor: Many things can cause swelling in the lymph nodes, or lymphadenopathy. It can be as simple as a localized infection to a much more serious problem. It needs to be investigated and you need to get some blood tests and possibly a biopsy of the lymph nodes if nothing else is found to be causing it.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.