How can you get pcitures and thoughts out of your head?

just to say for more information if needed im 11 and and male ok well i was watching Watchmen last night and there was this one sceane where the broke the bone of the bad guy like pulled it out of its socket and blood went everywhere and the bone came sticking out well today the thought and picture came in and instead of the guy doing that in the movie it was me and my baby sister and i dont know why somone plz tell me by the way srry i added this as answer im new