How to remove a stain from your ugg boots?

i lost one of my uggs for like month. i found it under my sisters bed yesterday :):)!! when i was looking at them i found a HUGE red spot on it, its bigger than i quarter but not much. i have NO idea what it is... i tried to remove it with a wet paper towel, it didn't work, but the paper towel was like a really light red so i think at least some of it came off.... im kinda freaking out becasue its almost winter... PLEASE HELP!!!!... thanks :) haha