On The Left Side Just Below My Last Rib...there Is

On the left side just below my last rib...there is a very small mass...half the size of a pea. I have been fighting a cold for the last 10 weeks and it is still hanging on. Could a virus cause these small lumps? I did talk to a doctor, and she said to keep an eye on it and it is most likely swollen lymph nodes from fighting a virus. Could that be the case? It is unpleasant...sore feeling... to touch it .