Nash went down with the injury in the first half after stepping on the foot of Portland point guard Damian Lillard. Nash started the third quarter, but pulled himself out of the game after the first possession. Nash had two points, four assists and four rebounds before exiting the game.
Nash recorded seven points and four assists in his debut with the Lakers last Tuesday.
The Lakers started the season 0-3 before defeating the Detroit Pistons, 108-79, on Sunday to get their first win of the season. Los Angeles is 1-1 without Nash.
Steve Blake has been starting in place of Nash, and is averaging seven points and four assists in the two games that Nash has missed. Second-year guard Darius Morris has been getting the backup point guard minutes for the Lakers.
Nash had two points, four rebounds and four assists against the Trail Blazers before the injury, after scoring seven points and dishing out four assists in the Lakers' season-opening loss to the Dallas Mavericks.
Nash said on Wednesday that he was "hopeful" to play in the rivalry between the two occupants of Staples Center.
Nash collided with Portland Trail Blazers' guard Damian Lillard on Wednesday in what was diagnosed as a shin bruise. The two-time MVP played only 16 minutes in the Portland game, 15 of which were before the injury. He returned in the second half for only a minute before Steve Blake replaced him for the remainder of the Lakers'116-106 loss
In two games to start the 2012-13 season, Nash is averaging 4.5 points, four assists and three rebounds per game. He scored seven points and had four assists in the season-opener, playing 34 minutes in a 99-91 loss to the Dallas Mavericks.
The Lakers' training staff said Nash injured his shin, and not his knee or ankle, but is expected to return in the second half, according to Mike Trudell of NBA.com.
The injury occurred after Nash had played 15 minutes against Portland. After scoring just seven points in his Lakers debut on Tuesday, Nash had scored two points on 1-of-3 shots before heading back to the locker room. He did, however, have four assists before leaving.
Steve Blake entered the game for Nash and played the rest of the second quarter. The injury is just the latest to hit the Lakers, who have also been dealing with injuries to Kobe Bryant and Dwight Howard.