Man, thats not good at all. What you have there looks to be bud rot. I had it once, caught it too late, it cost me my entire grow. It can spread (its a fungus) to your other plants, or other parts of the same plant. GOOD THING YOU CUT IT OFF! I hope none of the cut off parts touched any good parts.
What is your humididty? Do you have adiquate exhaust? Do you have a fan circulating air across your plant? Do you mist your plant? (Shouldn't be misting when bud is this dense) This is like cancer for your plant. Make sure you got all the infection off or it will spread and it is VERY BAD for you to smoke.
Sorry, good luck.
