James, 38, suffered the injury in Friday's 122-119 in-season tournament victory over the Suns in Phoenix. It occurred with 4:22 in the first quarter, when James drove to the basket and took an unintentional blow from Kevin Durant's knee on his left shin. James gathered himself on the baseline before receiving treatment on the bench.
After the game, James was seen walking with a slight limp, and he told reporters that his shin was sore.
"It never loosened up," James told reporters of the shin. "[It] pretty much locked up right then and there. So I tried to keep my composure, make sure I was OK and try to keep it stretched out and as loose as possible and play the game and be effective.
"Pretty sore right now. Obviously because the adrenaline is calming down and iced it, now it's pretty sore."
The Lakers have gotten off to a slow start this season, posting a 4-5 record entering Sunday's game against the 3-5 Trail Blazers. James is averaging a team-high 25.2 points, along with 8.4 rebounds and 5.4 assists, thus far in his 21st NBA season.