Before the disappointing 2-0 loss to Jordan in the Asian Cup semifinal on Feb. 6, a brawl between Son and Lee broke out, according to media reports.
Lee and several players reportedly rushed through a team meal so they could play table tennis.
Son, as the team captain, was not pleased with this action as meals before big games are often considered a time for bonding.
When Son asked Lee and other younger players to sit with the team, they said some disrespectful things to him. This resulted in a brawl, dislocating Son's finger.
Although Lee issued an apology to fans and teammates on Instagram last week, things have not cooled for the 23-year-old midfielder in South Korea.
For the past few days, South Korean netizens have constantly criticized Lee. Fans have even called for a boycott of brands that use Lee.
KT, one of South Korea's leading telecom companies, decided to remove Lee from their advertising campaign.
Lee signed a deal with KT in 2019 and renewed his contract last month.
On social media, many fans also signed an online petition, requesting the Korean Football Federation (KFA) to permanently ban Lee from playing for the national football team.
According to South Korean media, when the KFA reaches its conclusion, Lee will face a heavy punishment.
Lee is one of the top football talents in South Korea, after winning best player at the U20 World Cup in 2019. He is currently playing for France's biggest club PSG.
Son remained silent about the incident, and in his latest interview only talked about his club Tottenham Hotspur.