There are fears for the life of 28-year-old Abu Bakar, who was involved in a motorbike accident at the weekend.
Warning: Contains a graphic image
The stateless Rohingya refugee from Myanmar is understood to have life-threatening head injuries.
Doctors for Refugees believe he may die unless he is medically evacuated for more specialist care.
Friends of Mr Bakar, including Faisal Arkani, have been holding a bedside vigil.
"He is fighting last breath of his life," Mr Arkani said.
Mr Arkani provided photographs that show a man on a hospital bed with blood-soaked cotton in his right ear, a head wound and broken arm.
Mr Bakar was injured in the motorbike accident while on his way to work early on Saturday morning.
Mr Arkani said his friend's condition had worsened.
"He can't even open his mouth," Mr Arkani said.
Two CT scans have been performed but the results have not been disclosed.
Dr Barri Phatarfod, from Doctors for Refugees, said Mr Bakar needed treatment and care that was not available on Nauru.
"He needs to be medically evacuated out of Nauru immediately," she said.
"Bleeding from his ear, vomiting — these are really really ominous signs of a moderate to severe brain injury."
"He could die."
A spokesperson from the Department of Immigration and Border Protection said Mr Bakar was "receiving appropriate medical care".
"Decisions about medial transfers are made on a case by case basis according to clinical need in consultation with the contracted health services provider and the Government of Nauru," they said.
"The department does not comment on individual medical circumstances."