Karma is a man-made spiritual law, which dictates that any action, good or bad, brings upon oneself inevitable results, either in this life or in a reincarnation. Dreaming of karma suggests that we are aware of the consequences of our actions. Emotions in waking life are difficult to control. Through a belief in Karma we can use our dreams to help us gain control of those emotions. In pragmatic terms karma is the law of cause and effect what goes around comes around. When we have not always acted with integrity we may find that dreams warn us of what the effect might be.
Dreaming that bad karma is affecting you can mean you're feeling subject to an ultimate authority, or that you may have done or are contemplating something that will get you in trouble or bring bad karma. Take inventory of irresponsible or dishonest things you've done and make amends (apologize or take other action to make things right).