Sam first cut open his hand in Meet the New Boss when he remembers Hell, and falls on some broken glass. Dean bandages the wound. In Hello, Cruel World, Dean shows Sam how to use the pain from the scar to figure out what is real and what isn't. This is because pain in Hell is different from pain in real life. With this knowledge, Sam uses the pain from it to get rid of his hallucinations of Lucifer.
This seems to work for Sam so far. After the accident with the Leviathans, Sam zones out only once (The Girl Next Door), but is soon brought back by the pain from the scar. It is also briefly used and addressed in How to Win Friends and Influence Monsters when Sam is talking to Bobby how he's dealing with Hell. Sam begins to depend on the pain from the scar when Bobby's life is on the line in Death's Door.
In Repo Man, a case involving a demon they thought they had defeated years earlier. As Sam starts looking over reports Lucifer starts helping Sam with the case. Then after being unable to reach Dean, Lucifer's comments causes Sam to snap at him to "Shut Up". But desperate to find Dean, Sam lets Lucifer continue to help him with the case. This is the first time he had acknowledged Lucifer since he started using the scar to banish him. But by allowing Lucifer in once he was now no longer able to shut him out, making the power of the scar useless.
- Season 7
- Sam tried to rub this scar again in "Hunteri Heroici", implying that he feared that his current situation was also a hallucination.
- Sam is also shown, on various other occasions, to try and get out from certain, difficult moments by pressing onto his left palm. This includes Bobby's death, and Lucifer's possession of Castiel's body.
- In Season 12, Sam has cut open the scar on his left hand on three different occasions.
- At a convention, Jared Padalecki and Jensen Ackles commented on how Sam and Dean get bashed up but always heal. But this time with Sam's hand it didn't. They comment on how they had a joke about CW cream that healed everything, but it looks like they ran out. Sera Gamble also commented that this scar will be permanent.