odd one outGood morning, Odd one.
This is a good example of external influences upon dreaming. With your head under the covers, you got a hot, humid, smothering feeling. This feeling was incorporated into your dream as having a tiger biting your head. But there is still a meaning here, because your mind chose that particular symbol at that particular time. Let's go back and break it down a bit.
From what I've seen, anytime someone is riding in a car with others, the dream is fundamentally about the dreamer's relationship with the other people in the car, so it's likely that your mother and sister were direct representations of themselves in this dream. In terms of interpersonal relationships, to "have one's head bitten off" is a term which actually means, to be yelled at for some minor infraction, and have your words or actions taken all out of proportion with what's meant.
So, I believe that sometime recently, you said or did something concerning both your mother and sister, and you were shouted down for it. In this particular relationship, you feel simultaneously attacked, and smothered - you're feeling as if you need some more independence.