According to Neven, it was during the surgery that he was diagnosed with priapism - an unwanted, long-lasting and painful erection that is not accompanied by sexual desire.
The 45-year-old said: "I was in Iran for rhinoplasty for the documentary British Channel 4 is filming covering my life.
"We did not record the surgery but only the consultation sessions with the doctor. They gave me general anaesthesia and I reacted badly to it."
The reality TV star recovered in a hospital in Serbian capital Belgrade, but said he was refused painkillers despite being in agony.
He said: "I'm currently residing in Belgrade hospital since Friday. Unfortunately, I don't get analgesics because they do not give them to patients here, so I continue to suffer.
"I have to be at the hospital for five more days."
But Neven said another operation has relieved him of his priapism, though he will not be fully recovered for several months.