pain under my arm

i dont know what to do. im starting to get nervous and dont know wo to see or what to do. what could it be>?

Re: pain under my arm

Could be a swollen lymph node or a pulled muscle. I had this last month and I thought it was a "lump" but it was under my armpit kind of in my ribs and I went to my ob/gyn and he said it was a pulled intercoastal muscle.