Miller was hurt when he was checked by Washington's T.J. Oshie in the third period. Miller, who had an assist Monday, finished the game and had plugs stuffed in his nose to stop the bleeding.
Gallant was unhappy with the hit that caused Miller's injury.
"Hopefully everybody's seen [the hit] and said, 'Where's the call there?'" Gallant said.
The Golden Knights trail the Capitals 3-1, with Game 5 on Thursday in Las Vegas.