My 14 month old has a lump on her left ribcage, close to her sternum (but clearly on a rib). It's hard and immobile; it feels like it's part of her bone. She doesn't seem to have any pain when we feel it, and you can feel the skin sliding over top of it. I only noticed it a few days ago, but it appears to be staying the same size. Her behaviour hasn't changed recently; though she recently went through a huge growth spurt, and tends to be a bit more tired than she used to be. We have a regular check up with our family doctor in a few weeks, should I get it checked out in the meantime?