Visions of Hell Realm in Contemplation- What does it mean Yesterday while reading a book suddenly my mind generated the following visions: I saw a girl in a white dress being tortured in this very unpleasant place which smelled bad and was horrible , I saw her being raped by this creature who looked horrific , again and again these visions came to me in the night. 

What could these visions mean ? Are they trying to warn me of some bad karma ripening. As it is said by many Tibetan teachers that they get warnings of future happenings in dreams. Although this was not a dream.
Some relevant advice here (from Awareness Itself -- Visions &amp; Signs) by Ajaan Fuang:


  § "Don't have anything to do with the past or the future. Just stay
  with the present — that's enough. And even though that's where you're
  supposed to stay, you're not supposed to latch onto it. So why do
  think you should latch on to things where you're not even supposed to
  stay?"
  
  § "You know that you shouldn't believe even your own visions, so why
  go believing the visions of others?"
  
  § "If you can't let go of your visions, you'll never gain release."
  
  § One of Ajaan Fuang's students asked him, "When you see something in
  a vision, how can you know whether it's true or false?"
  
  His answer: "Even when it's true, it's true only in terms of
  convention. You have to get your mind beyond both true and false."
  
  § "The purpose of the practice is to make the heart pure. All these
  other things are just games and entertainment."