Amin, who has just been called up to Egypt's squad, was substituted on 15 minutes in the Pharaohs' 4-0 friendly win over Mauritius on Friday after colliding with the keeper.
His injury was initially thought to be negligible, but eventually it turned out to be quite serious.
"Right after I was taken off, Egypt's medical staff told me it's just a minor problem that will keep me out of action for four weeks," Amin, who has scored five league goals this season, told FilGoal.com.
"But I noticed that my knee evidently swelled up in the next day.
"When I went to Gaish, the technical staff told me to undergo X-ray checks in order to get the full extent of the injury determined.
"The X-ray images showed that the anterior ligament has been damaged.
"I will have a splint put on my leg for four weeks, then undergo surgery to repair the cruciate ligament."
On his way to the dugout during Friday's game, Amin was spotted while shedding tears for missing out on the opportunity to prove his worth on his international debut.
Egypt coach Hassan Shehata gave him a shoulder to cry on when he got off the pitch.
"I wish I had impressed on my first appearance with the national team," he added.