What Causes Swelling In The Left Side Of The Chest Along With Intermittent Pinching Pain At The Armpit?

Hi, my son 28 years old been having an issue where left side of his chest got a bit swollen. He went to doctor two weeks ago and was told might be inflamed so told to take ibuprofen for a week. He did now he says its spread out to under his armpit and he feels like a pinch every now and again under his arm. He has another appt tomorrow to see a different doctor. Any ideas?