Could Fluttering Feeling In Chest Be Due To Trapped Air Or Blood Clot?

Last Sunday, I fell landing on my left rib cage. I had no fracture, but was told I have torn cartilage and taking hydrocodone for pain. I have started to experience what feels like a flutter or something move almost like a baby would kick in the ribs. I am not pregnant as I had a hysterectomy last February. What can this feeling be? Trapped air, blood clot, etc. And could it be serious