Greetings, I am a 28 y/o male, healthy as far as I know. I feel a very slight pain in my left armpit when I stretch the shoulder (pull arm up or outward). The pain goes away immediately after putting the arm down and happens under the skin, not on it; it feels like something was being pulled. It started over a month ago but only in the last week or so has become more noticeable for me. There are no rashes or other markings on the skin, and no lumps, inflamed lymph nodes, or other notable changes in the area. Is this a cause of concern? Thank you