When the coral's "skin" gets damaged, it will leak its entrails out the opening, which for a dendro are bright yellow. It should heal up pretty fast. Mine did the same thing since I had to handle it alot to get it into its location, I ended up causing some small nicks in its skin around its base, just from touching it. It healed up completely within a couple days.
I had three heads to start. When i was placing it, it got four nicks in it. I had seven heads after two weeks. only three of those survived for a total of six.