Rib pain feels like a soreness and tenderness of the ribs. You usually feel it on the right side below your breast. The pain is usually exacerbated when you sit down. Rib pain usually only happens in the third trimester.
As your womb rises in your abdomen, your ribs get compressed. Your baby may also be bruising your lower ribs with his/her head or by punching and kicking you in the ribs. Don't worry, the baby doesn't mean any harm!