I think i have to agree so far with Melissa sunburn can do that and where it is on the caudex is on the high side. BUT please please please check it that its not mushy under that. like Doris said if it is Mushy you need to take care of that if it feels firm then it should not be rot. I think if it is sunburn i would not clean it up to much mabe a little but i like it when they have interesting marks and this mite in a few months drop some of the peeling and look cool.
you can clean up at any time as long as it you cut into good flesh DO use Cinnamon and dont allow it to rain on it for several days.
Now i like that pot you have it in BUT its a glazed pot so it will not loose much water. so take caution on watering. Also if and when you take a knife to it for any reason make sure you use something to sterilize the blade between every cut so you don't spread rot or disease.
Yes im long winded but i try to explain everything and WHY so you can better understand these plants
so next i see is that pot has a saucer when you water or it rains make sure you empty that or you can get root rot fast.
And do please keep us informed
mike
