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

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