It sounds quite positive and
Lautaro Martinez himself said that he only needs a few days to recover and then will be back as soon as possible. He also mentioned that a streak of 89 games in a row with missing a single one came to an end now. That's really a good number for any player. This makes him so valuable because his team can rely on him, can count on him. If nothing unexpected is reported, I think he will miss the game against Lecce and then he will be back. The Champions League games are definitely not at risk here.
Inter Milan head coach Simone Inzaghi have confirmed with Lutaro Martinez absent on upcoming Serie A match when Inter Milan against Lecce and Inzaghi have called youth primavera players Amadou Sarr for joining to main squad against for match against Lecce. Personally its good side with Lutaro Martinez injured because he get many time getting rest after filling regular position on every Inter Milan match and Champion League round of 16 will play two months later he has time recovery as soon possible.
Champion League match still have many days left and some European players get faster recovery from their injury, however not official announce with Lutaro Martinez with serious injury and likely he will be ready against Atletico Madrid.