When someone else on this forum had a bad DMT experience, I made the following remarks:
original_sessions wrote:As the alchemists of old would state: "As above so below". Being such, since everything in this universe is connected and one with itself, nothing is as bad as we perceive it to be. If everything is one, then even entities like demons, devils, etc. are really nothing more than extensions of the human mind. Next time you find yourself in a state of fright, try to remember that however weird or "evil" something seems to you, it is just your cultural perception that makes it seem that way. "Nothing is" as RAW once stated. "It is only what it seems to me at that particular moment." Good luck to you on your journeys.
I agree with ۩ in the sense that nightmares are really just an end result of our subconscious mind being overly active, throwing random and indecipherable symbols at us sporadically, without any point or purpose.
According to webmd.com, nightmares can be caused by late-night snacking (which can increase metabolism and signal the brain to be more active); medication; intake of alcohol; withdrawal from various substances; and/or anxiety/stress. Also, the site noted that "while it's true nightmares are more common among children, one out of every two adults has nightmares on occasion. And between 2% and 8% of the adult population is plagued by nightmares."
Other sources state that nearly 75% of the emotions that we experience in dreams are negative 
Then, again, NPR (IMO) has never been that good of a source to cite.
As such, I wouldn't worry too much about it. Nightmares are pretty normal. I'm sure it'll all clear up in a few days or so. Until then, pleasant dreams and best wishes.
my smile is stuck / i cannot go back to your frownland / my spirit is made up of the ocean / and the sky and the sun and the moon / and all my eye can see / i cannot go back to your land of gloom / where black jagged shadows / remind me of the coming of your doom / i want my own land / take my hand and come with me / it's not too late for you / it's not too late for me / to find my homeland / where a man can stand by another man / without an ego flying / with no man lying / and no one dying by an earthly hand / let the devils burn and the beggar learn / and the little girls that live in those old worlds / take my kind hand / my smile is stuck / i cannot go back to your frownland / i cannot go back to your frownland