With internal experiences, we must always analyze them scientifically and with clarity. Who was the man that was warning you? That is something you might need to figure out, because the objectivity of the experience depends upon the clarity of your perception and the application of the dream to your physical life. If the dream remains unclear, you might want to be patient before passing judgment that you are a victim of an attack.
Personally, I do not know if having a black mark determines that you are being attacked. After more than a decade of experience being attacked in the internal planes, I can say that if you suspect you are a victim of black magic, you must exercise tremendous patience, because many times we may just be the victim of our own minds. Be patient, and meditate on it, because experience will show you whether the dream is real or not, and as to what it means.
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"