What Does Swollen Lymph Nodes Under Armpits Indicate?

Hi, I m a healthy 25 year old female who about a month ago felt two bumps under my left armpit. I had recently had routine bloodwoork done and all of my tests were normal. I visited my doctor who said he could not feel the lumps that I was talking about and sent me to a general surgeon. The general surgeon said that my lumps were just swollen lymph nodes (they are both moveable beneath my skin) and not to worry about it. One is about the size of a nickel but flatter and more oblong in shape and the other is a size of a pea. I know that swollen lymph nodes can be a sign of cancer and so I m wondering if I should be worried when and if they do not decrease in sign. The general surgeon was not at all concerned (he didn t order a biopsy) but I just want to make sure that I m not being foolish by not getting a second opinion. The smaller swollen lymph node has slightly decreased in size over the past few weeks but the large one does not seem to have significantly decreased.