I swallowed a open staple by accident what should i do?

Call your doctor: It is unlikely that his will cause any harm. That said since it is a sharp item there is a slight chance that it might lodge in the soft lining of your GI tract. Let your doctor know, an x-ray can detect the location of the staple and can make sure it has passed. If you have any throat or abdominal pain be seen asap.

Don't worry: Generally it is more likely than not that sharp objects will be pass through the intestine and out in the stool without any problems. This is not uncommon, especially in children. Injury to the oesophagus would cause throat or chest pain made worse with swallowing. Obstruction of intestine will present as abdominal pain +/- distension, nausea & vomiting. If you develops these signs, go to the A&E.