“How long does the pain last after an endoscopy?”

It really depends on what was done during the procedure. If it was just looking, then you shouldn't have any pain. It is not unusual to have minor discomfort from the scope that was slid down your throat if your esophagus was unusually small. However, this will go away in a day or 2.
If you are having severe pain, bleeding, or severe difficulty breathing or swallowing, you should go immediately to the hospital. Follow up with your surgeon/Doctor.

Resolve within 48 hours Post endoscopy but remember it varies from human to human.