I Found A Lump In My Armpit About Five Days

I found a lump in my armpit about five days ago. There is no discoloration or pain, even when I press on it. I tried moving it around but it only moves a couple of millimeters in either direction. I have not been sick for many months, and I have never had cancer, HIV, etc. I am a 35 yrs. old, white male, in generally good health.