What type of liability do I have if my dog knocks someone down?

I am in California...

My dog was out in our front yard, off leash, when a child about the age of 5 or 6 came walking down the street with his older brother. They spotted the dog, started screaming & took off running, prompting my dog to follow after, thinking it was play time. My dog is in no way aggressive, he is well socialized but is a young, exuberant Boxer mix. Anyway, the kid turned around to see if my dog was close to him, stumbled over his own feet & began to fall down. My dog then jumped at him and his 2 front paws came down on the boy's upper arm basically pushing him down, although he was already falling. The mom, who was nowhere to be found during all this, except after her child fell down, called 911 and a fire engine, including paramedics, 2 cops & animal control responded. The child has 3 pinhead-sized blood bruises on his upper arm, caused I believe by my dog's paws. There were no puncture wounds, no scratches, it did not break the skin at all, no blood. The woman reported it as a dog bite however. The paramedics rendered no medical aid, the mom refused transport to a hospital & animal control did not quarantine my dog since it did not break the skin but they cited us for having an unlicensed dog. The mother told the officers she was taking her child to the doctor "because he hurt his leg when the dog knocked him down".

My questions is, does she have any real grounds to sue and if so, what sort of liability am I looking at? I am trying to avoid, at all costs, a claim on my homeowner's insurance policy. I also have 2 signed witness statements which say the dog never bit the child nor was he acting in an aggressive manner to anyone.