Howard said at first he "thought it was a stinger" after Caron Butler came down on the Lakers center's shoulder.
Howard called it a sprained rotator cuff and said he's a "game-day decision."
Coach Mike D'Antoni didn't seem to be worried, saying the chances that Howard would play are "good."
Howard said he woke up extremely sore. He skipped practice Saturday and received treatment from the Lakers' training staff.
The Lakers (15-17) are currently in 11th place in the Western Conference standings, two games behind the Portland Trail Blazers (17-15) and Nuggets (18-16), who are in seventh and eighth, respectively. A victory Sunday would give the Lakers a 2-1 series lead over the Nuggets with a final matchup Feb. 25 in Denver.