見てられん＝見ていられない＝I can't stand watching it anymore. You say it when... 1. Someone is acting nonsense. you can't stand watching his act anymore. you probably just leave or stop this nonsense. 2. Someone is pitiful. you can't stand watching his act anymore. you probably just leave or go to help him. 3. Something awkward is happened. I can't stand watching it anymore. I'm japanese learner too. Hope this help.