The ex-Lille man walked off in the second half after a clash of heads with Milan Skriniar after they both contested for the same ball.
Although Osimhen walked off without the help of a stretcher, the injury took him out of action for two months, with the Nigerian needing surgery to fix his broken bones.
Initially, the injury was thought to be nothing serious, but Osimhen has now revealed the pain he went through, saying he had a near-death experience.
Speaking in a pidgin interview on Wazobia FM, the Super Eagles star revealed he found it difficult to sleep and eat after his surgery.
"That injury I had against Inter Milan was like a near-death injury," Osimhen said on Wazobia FM.
"I am the only one that felt it, and I can only speak about how I felt because it was my face and body.
"But to be able to stand up without using the stretcher, walk out of the pitch on my own, then I knew that it was something I could handle.
"For me, as I got to the hospital, I told my doctor that I would be out for two weeks maximum.
Osimhen's strong mentality helped him
However, Osimhen revealed that he realised he would be out for a long time after the scan came out.
"When the scan came out, I fractured many bones, which they had to remove and fix inside again.
"I have like 18 screws under my jaw. I went through a lot.
"A lot of sleepless nights. I could not sleep, I could not eat with the pain.
"But at the end of the day, I am a lion, and I know the kind of mentality I have.
"In my mind, I had already scheduled my return following the surgery," Osimhen added.
Despite the challenge he had, last season was Osimhen's best ever in Europe's top five leagues. The Super Eagles star scored 14 league goals in the Italian topflight, beating the 13 goals he scored in his lone season at Lille.
NB: The quotes were edited and translated from Nigerian pidgin.