What Causes Pain In Under Arms?

Hi, my underarms have been sore for about a week. I had bronchitis a few weeks back and have been better for about a week. I'm thinking that it's swollen lymph nodes, but I don't feel a thing when I feel under my arms. I'm touching them constantly and think I have made them sore. I don't notice the soreness when I'm not wearing a shirt. There is not redness, bumps, lumps, etc.