Superhuman Durability: Johnny Blaze is highly resistant to the point of being basically immune to all types of earthly physical damage as he has taken blows from beings such as an enraged World War Hulk with no sign of pain or discomfort, had his entire skull destroyed and regenerated instantly without any discomfort, and while the Ghost Rider is in control only divine weapons forged in heaven can cause discomfort or harm to the Ghost Rider. The Ghost Rider is capable of withstanding great impact forces, temperature and pressure extremes, powerful energy blasts, and falls from great heights without sustaining injury. As his bodily tissues have been transformed, leaving only a skeleton, most projectiles such as bullets simply pass through him or bounce off his bones. Ghost Rider's body is for all intents immune to physical injury, as he is evidently not able to feel pain and is able to survive with no apparent discomfort no matter how severe the injury (Unless a weapon forged from Heaven itself is used against him, which would be a problem).
Regenerative Healing Factor: Despite his invulnerability to conventional forms of injury, objects such as weapons forged in heaven by the arch angel Zadkiel, can actually harm the Ghost Rider to a certain extent. However, if his being is damaged, the magical energies imbuing him allows the Ghost Rider or Johnny Blaze to instantly regenerate any and all damage done, even to the point of fully regenerating lost limbs in moments, and regenerating his skull after it was destroyed in seconds without any discomfort or any evident pain.
Psyga315 said
seriously, skull-themed characters are almost always a bad sign