Open Question: Lymph node was swollen for about 10 days, then shrunk significantly?

For about 10 days I had a painless, rubbery-feeling lymph node in my left armpit. It was nearly 2.5 centimeters then, and after those 10 days (and in the 5 weeks since then) became just under a centimeter; you REALLY have to look for it to find it now, but it's still there. I'm worried it could be lymphoma? Surely, if it shrank and doesn't seem to be coming back, it couldn't be lymphoma?