What Does A Large Lump In The Right Armpit Indicate?

Hi I have a large lump in my right armpit, I can ony feel it when I raise my arm or tough the back of my head it gets bigger. I m right handed and the lump is bigger on the right compared to my left. I have two - one in each armpit both in the same place. It feel like its part of my back or shoulder muscle. It s hard and only hurts after I ve touched it for a little while an sometimes gets bigger the more I touch. They ve been there for a year since I started weight training and not sure if its anything serious or part of my muscle? I ve recently had a blood test and failed slightly on one of the parts - the infection part but only by 0.4. Quite worried but I m perfectly healthy I play tennis a least 3 times a week just my armpit aches where the lump is the day after.