May be a st thomas mushroom but pic is a bit blue and image is a bit distant to confirm.
Please keep in mind- This is NOT an emergency. There are a few of us who respond to an emergency and posts like this take away from those who need an immediate response.
An emergency is a crisis situation in which someone is losing all their fish, a fish illness. coral is getting wiped out, accidental overdose of medication or additive as examples.
If you can post pics closer under white lights, you will get that precise answer you are seeking