Flank pain that comes and goes is not a symptom of lymphoma as far as I know. The fact that your lymph node got smaller almost rules it out. I have many palpable lymph nodes in my neck and armpit. As long as they are not larger than 2.5cm and remain static in size you have nothing to worry about. I had a lymphoma scare as well, today I've also been experiencing a stabbing flank pain. Occasional pains are normal for everyone. As long as they aren't severe,persistent(10+mins),or accompanied by other symptoms like fever you are most likely fine.