This girl is starting a rumor about me that I got beat up? How do I stop this?

This girl is starting a rumor about me that I got beat up? How do I stop this?
Yesterday, when I was walking down the halls this guy puts me in a headlock but it was playfull, but this girl so it and thought it was a real fight, so now she is telling everyone, how do I stop this? And when they ask the guy who put me in the headlock if it is real , he sometimes says yes and sometimes no, but we are cool, but how do I stop this rumor?