Bump under armpit

About a month ago I started feeling a bump under my armpit, It hurts when I press it. I'm 50+ years old. It is in the left arm. I checked my left breast thoroughly for any lump but there is nothing there. It is in the back of my breast but more likely to the side under the shaved part of my armpit. It kind of presses some nervous point because the pain goes to my arm when I move it. It gets worst if I don't sleep well. Insomnia happens to me sometimes. When I sleep fine, it looks as it gets away. For some reasons I do not have access to a doctor. I am concerned. Can you help me?