The xenomorph's dome head is hurt, it could have been shot by Raines or one of the other characters with the prototype pulse rifle on the space station.
This scene must have been to visualize the xenomorph's ability to regenerate quickly and heal wounds without leaving a mark. Making the movie's main characters more scared when they face the unkillable beast. Let every viewer of this film realize the nature of horror film and change their opinion about the xenomorph and Alien franchise.
The ability to regenerate was spelled out in the script of original Alien, and Ridley Scott said that crushed xenomorph could DNA back to parts and regrow in the director's commentary audio track for Alien: Covenant. Many stuff of script was actually filmed, just deleted, and can be found the deleted stuff related to the deleted/alternate scenes included in the disc or the unused footages in behind-the-scenes.
