Is there anything wrong with having black spots on my canker sore? This is the first time ever that I had those. Yes, the dark spots are on the white surface of my canker sore NOT ON THE TONGUE , NOT ON THE LIPS , NOT ON THE CHEEKS but ON THE CANKER SORE. You see, I was applying alum and then, suddenly I was so surprised to see a black thing in there. I washed my mouth and saw that there were spots. What should I do? Is this normal?