Dreaming of anger means you are currently repressing those emotions in the waking hours. The hostilities you hold toward the person in your dreams are never at the receiving end of a yelling match in the waking hours because you cannot conjure up the balls to do it.
Holding the pent up anger inside you is not healthy and will lead to a greater destructive outcome. Get it over with by confronting the person that causes you to have restless nights.