What Causes A Painful Lump Below The Armpit?

I have noticed a strange sensation on the left side of my breast (I m a female aged 52). I have fibrous breasts so finding a lump is a little challenging. I have found what feels more like a gland on the breast itself, the area close to the chest and just below the armpit. IS there a gland that I would feel in that location? It s tiny but if I manipulate it I get an odd sensation, which is just a slight soreness. (I know this is probably impossible to answer but I recently moved and haven t a family physician up here and really don t want to go to emergency if it s just a gland acting up. Note I m pretty tired - it s been a long year and a very cold winter.)