Looks like it might be one or more barnacles. Shouldn't hurt anything....may or may not have survived the coral's transition from wild to domestic. It'll have a feathery appendage repeatedly fanning the water if it's alive. No worries if it's not alive tho.
I tried to scrap it off but it appears that is part of the trumpet. It appeared about a week ago. When I tried to scrape it off it felt like it was tissue with bones.