I have an inflammation in limf nodes which brings me a lot of pain. What should I do? It continues for 2 weeks!

Infection-antibiotic. You probably have infection in lymph nodes or the tissues connected to those lymph nodes. It is important to see your doctor for treatment to prevent the development of abscesses and lymph edema.
Monitoring Centers. 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.