There aren't a lot of rules when it comes to loose balls in the NBA, but regardless of how physical things usually get, landing an elbow to the chin of an opposing player comes off looking pretty dirty.
You could argue that Justin Anderson had no intent to elbow Russell Westbrook. That he was merely a bit off-balance as he went for a loose ball, and that this sort of thing happens when players get on the floor.
You could also argue that Anderson's elbow appeared to be a subtle, yet intentional shot at an opponent in what has been a very feisty series.
Westbrook certainly appeared to agree with that argument as he wasn't too thrilled with the play.