Wallace scored 15 points before a flagrant foul by Andrew Bynum knocked him to the floor with 2:08 left in the fourth quarter Tuesday night in the Bobcats' 117-110 win.
A statement Wednesday from the Bobcats said Wallace was taken off the floor and underwent X-rays at Staples Center. Preliminary results were inconclusive, prompting Lakers team physicians to arrange a second examination.
Wallace had 30 to 40 percent of his left lung collapse as well as a non-displaced fracture of the fifth rib. The team said Wallace underwent a CT scan in Los Angeles, and had a chest tube inserted into the lung to help restore full function.
Wallace was to remain in the hospital over the next 48 hours for observation and did not accompany the team to Portland for Wednesday night's game.
Team spokesman B.J. Evans said there was no immediate indication on when Wallace would rejoin the team, or even when he would return to Charlotte. Veteran forward Juwan Howard replaced Wallace in the starting lineup game against Portland.
Charlotte coach Larry Brown said he did not think the foul was malicious, nor did he believe that the NBA should take action against Bynum.
Bobcats guard Raymond Felton, who was on the floor during the play, said, "I'm not going to make a big assumption, but was it a hard foul? No question. But I don't think Andrew Bynum was trying to hurt somebody."
Lakers spokesman John Black declined to comment on Bynum's actions, although he said, "It wouldn't surprise us if we were to hear from the league."
In 41 games this season, the 6-foot-7 Wallace was averaging 16.4 points and 7.4 rebounds per game for the Bobcats, who beat the Lakers for the fifth time in their last six games against each other. Charlotte's victory was just its sixth on the road against 13 losses.