@Laotionne - You may have a pulled muscle as your grandmother said, but the rib pain from bruised ribs is often confused with a pulled muscle in that general location. The injuries sometimes happen in the same way, so determining which injury you experienced can be tough sometimes.
With bruised ribs, the cartilage that holds the ribs together is what is actually damaged. With bruised ribs, you can also have back and rib pain when you move, similar to what you have with a pulled muscle. Also, if you have more pain when you breathe then this is a strong sign that you may have bruised a rib. Either injury can be painful, and they sometimes go hand-in-hand, so that is another possibility.