Golden ball cactus question?

Question:I have a golden ball cactus. I did something to it that made it go brown near the top. It was a pretty big brown mark and I'm pretty sure that that part is dead. It's about 1 1/2 inches long and 3/4 inches tall. It is also near the top of the cactus. Now, at the top, there are all of this white fluffy stuff and it could be a flower. Will this mark affect how the cactus grows andis the cactus dead even though most of it is green with the small yellow spike things. Just in case, I got this at the Desert Botanical Gardens in Phoenix and live in the Western suberbs of Chicago.

Answers:
Two things come to mind. You may have watered it during the winter months, which it can't stand, and rotted the top. Or you watered it and left it to frost, which could have done the same. If you let it go, cacti have tremendous healing power. It will probably always be scarred, but will heal itself and grow beyond it. I would put it in a garage or in the house during the winter,and don't water during this time.