In the scene where The Predator and Alexa Woods are about to go back to the surface on the lift. You see an alien pierce through The Predator’s right shoulder with his tail. Now fast-forward a little bit too where they stop running from the collapsing ice. When The Predator stands up to survey the damage of the area, you see there is no wound or blood on his right shoulder. But when he turns to Alexa to take off his helmet, you see the blood.