What Is The Treatment For Scratches On The Stomach?

1 week ago my 14 yr old daughter was playing on a zip line in a friends back yard and ended up dragging her body on the ground until a cement stepping stone to her stomach stopped her. she has a lot of scratches on her stomach and now has a gumball size hard knot under the skin directly under the scratches. should I be worried or will it go away in time?