What Causes Rib Knot Painful Feelings With Stomach And Back Pain?

Ummm dude one of my friends has like a small knot feeling in between her ribs and when she bends down it POPS an it really hurts her. She hasnt been able to eat because it makes her belly hurt really bad. The pain starts in her back but then it lead to her belly and now between her ribs I think its on her left side that hurts. It sounds like a tumor to me but I dont know and I hope not.