My Dog Left A Bruise On A Lady's Kid And She Is Telling Me I Need To File A Police Report And Will Be Responsible For All Fees From Her Child's Er Visit

Location: Denver, CO

I was walking my leashed dog (I'll call him Henry) in my apartment complex when a lady and her four kids ran across the street - not on the crosswalk - to get to the same sidewalk I was on. A car was driving down the same way, so I could not move off the sidewalk to let them pass as I normally would (not because Henry is mean or aggressive, but because I don't know how the other people will react to a big dog.) Her kids tried to run past me and Henry, and he got excited and jumped on one of them, leaving what appeared to be a bruise on her child's stomach. He has never done anything like this before. The child started crying, saying that Henry bit her, and her mother started saying they needed to go to the ER after looking at it. I didn't see any broken skin, and was able to immediately pull Henry back to my side, where he dutifully stayed. He did not strain against the leash or make any attempts to harm any of her children. I exchanged numbers with the mother, and sent her the vet records to prove that Henry has all of his vaccinations. She texted me afterwards telling me I needed to file a police report, send her a copy of it, and that I will also be responsible for the bills from the ER visit. The child was understandably upset, but able to walk and communicate with her mom, and I did not see any blood. I have already looked at the Colorado law about dog attacks (Section 13-21-124, Civil actions against dog owners) and am 99% positive that the bruise my dog left is not serious enough to warrant any legal action or leave me liable for her ER bills, but I've never dealt with this before. I haven't responded to the mother or said anything since sending over the vet records. Do I need to get a lawyer involved, or file a police report? What if the mother files and makes exaggerated claims against Henry?