Chile coach Reinaldo Rueda had suggested Sanchez – who is on loan at Inter from Manchester United – could be set to miss "two to three months" after suffering an ankle injury in Saturday's friendly with Colombia.
The forward had further tests upon his return to Milan, with the results of those examinations confirming Sanchez has dislocated his ankle.
"Sanchez underwent medical tests earlier this morning at the Humanitas Institute in Rozzano," read a statement from Inter.
"Results revealed a joint dislocation in his left ankle which has caused damage to the peroneus longus tendon."
Sanchez will now travel to Barcelona for consultations with professor Ramon Cugat, who has often treated injured Manchester City players, including Benjamin Mendy and Kevin De Bruyne, to determine whether an operation will be required.
Former Arsenal star Sanchez has made four appearances for Antonio Conte's side this term, scoring one goal in Serie A, though he was sent off later in that match against Sampdoria.