Aguero has been involved in a car crash involving his taxi and a lamp post.
The player has confirmed he's suffered a broken rib and is in pain.
Aguero will miss this weekend's clash with Chelsea - and up to months of action for Man City.
The striker was in Amsterdam at a concert headlined by Colombian artist Maluma.
Reports suggests he was wearing a seat belt, which saved him from more severe injuries.
Argentine outlet TYC Sports say the 29-year-old was on his way back to the airport but has been taken to a local hospital for treatment.
Aguero will miss the Premier League clash at Stamford Bridge and Argentina's World Cup Qualifying ties against Peru and Ecuador at the start of October.
If the striker is ruled out for the all of next month, he'll also miss games against Stoke, Napoli, Burnley, Wolves and West Brom.
Man City also play Napoli, Arsenal, Leicester, Feyenoord, Huddersfield and Southampton in November if Aguero's rib injury takes longer to heal.
Manchester City said in a statement on Friday morning: "Sergio Aguero will be assessed by Club doctors today after being involved in a road accident on Thursday.
"The City forward was in Holland on his day off and has sustained injuries.
"He will return to Manchester this morning and his status will be checked ahead of tomorrow's Premier League clash at Chelsea."
Aguero himself told Radio Metro de Argentina: "The taxi driver did not see the curve and skid. And when he skidded, we hit the pole.
"I broke my rib, now I'm resting. It hurts me badly. I'll be discharged in a little while."
Former club Independiente reacted to the news with a tweet wishing the forward well, saying: "Strength and quick recovery. All Independiente is with you in this difficult time".
Aguero has scored seven times for Pep Guardiola's side in all competitions this season.
The news comes after Man City team-mate Benjamin Mendy revealed he could be out for the remainder of the season after rupturing knee ligaments.
Gabriel Jesus will be expected to lead the City line in Aguero's absence.
