Whats the likeliness the a lymph node in the groin area is a sign of hiv?

Lymph node in groin: Very unlikely unless you are HIV positie.

Many, many causes: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells and digested food. Lymph nodes "taste" the lymph for anything bad 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.