Dreams can be frightening, but they really do not have a relation to real life. It is possible that you have this dream because you have some fear, or have had an experience which matches up with this nightmare.

But really, dreams are just the brain's way of processing things while you sleep. I have 3 seriously recurring dreams which have no basis in real life and dream every night about crazy things.

1. I am in school and have either missed doing work and not graduating, or not being able to remember the combination to my locker, or can't find it.

2. I cannot find my car in the parking lot. Or know the person that stole it and spend my dream trying to get it back.

3. My teeth crunch in my mouth and fall out.

I am empathetic to your nightmares, though.