Pain in armpit. Type of inflammation?

Hello, my left armpit had been feeling a bit uncomfortable for the past month or so. The other day as i was massaging the area, I feel quiet a few rice-grain sized lumps which i assume to be my lymph nodes. None of them were swollen however 1 or 2 of them were very painful and tender when i pressed on them even though they were not swollen and couldn't be seen otherwise. A week ago, similar discomfort started in my right armpit and i found the same thing, no swelling but 1 point was tender and painful. I've also found a similar point but a bit rounder near my inner elbow on my left arm. What causes painful lymph nodes without swelling? Or could be some other type of inflammation? They are small like a rice-grain, not very hard to touch, painful when pressed, and I think are movable. Kindly advise, thank you.