I was in a car accident in January. I fractured two ribs on my left side. I'm healing very well, with no pain in my ribs, but there is a mass about the size of a softball under my left ribs. I had an ultrasound, which showed nothing. There is no pain, either. It is a soft mass. I'd been using walking aids (walkers, crutches, canes) up until last week. I just got full weight-bearing privileges. What IS this blob? My docs keep telling me it will dissipate, but I'm skeptical. Thanks.