Donovan McGowan, 18, had the piece of metal removed by surgeons in Glasgow on Wednesday after living with it inside his skull for two months.
It was discovered when Mr McGowan, who said he was “in agony”, asked for a scan.
The bolt was left in March when Mr McGowan had plates fitted on his skull at the Southern General Hospital after being hit by a car.
The father of one from Glasgow told the Scottish Sun newspaper: “They said: ‘this is quite embarrassing but there is something metallic like a tube still in your head from the operation’.”
“It’s been more than embarrassing for me having to walk about with this lump on my head.”
A spokeswoman for NHS Greater Glasgow and Clyde said yesterday: “We have offered a full apology to the patient for this unfortunate error.
“A full review of our procedures is under way to establish what happened and to identify steps to ensure this does not happen again.”
Mr McGowan underwent surgery in February after suffering head injuries in a road accident.
A month later he had another operation to fit the plates but doctors left the swab, described as looking like a cotton bud but made out of metal and cloth, behind.
The teenager told the Sun he had to give up his job as a steward at Celtic Park because of the pain and may seek compensation.