Blood Money - S5-E9
Continuity mistake: After Walt comes back to Jesse's house and returns his bags of money to him, Jesse is sitting on the couch with his hand over his mouth as he looks off to the side. After Walt says that "it's your money, you've earned it" he goes to sit down on the couch with Jesse, his hand still over his mouth as the camera pans around. When it cuts to a different angle as Walt is sitting down, suddenly Jesse's hand is down on his neck.
Chosen answer: It is part of the ritual for la Santa Muerte. It is a sign of humility and sacrifice.
djm