How to stop a rumor about you?

There has been a big gossip going around the school, not just middle school but high school and elementally that the 6th graders can't go to the camp this year because I kissed max and was caught. Yes I did kiss him but it was forced and 2 other people made out. It was only a second and it was forced. I am so pissed because my mom said that an 11th grader went up to my sister Shira and said your sister kissed a boy at the camp and was caught so now they can't go. I have no idea who to stop this bull shit. Can anyone help