Why i have a lump under my armpit

Found a lump under my armpit. Initially it was miniature. The pain was not felt. Now rub and growing. My friends such do not. Recently found out that it can be serious malaise. But I think, obviously fatty lump. Found understandable information about this lump. Now I'm not afraid of terrible diagnosis. Everything is clear and detail is written down to the smallest detail. Many have problems with the armpits. There are a lot of microbes. Then arise balls. They can be painful, but not always. It is better to know in advance about this problem. In this case there will be no fear of horror. Good, that now I understand this. small painful lump under armpit