What is this polyp looking thing?

[GothFishKeeper]

A couple weeks ago I added a half pound piece of live rock to my nano as an island for the mushroom I’m planning on adding. Today I noticed this really small thing that looks kind of like a polyp on the rock near a hole. Any idea what it could be? There’s also a similar looking one towards the back of the rock as seen in the second picture. They both flow with the current and occasionally close up really fast as if they’re trying to catch things. The video I’m attaching is a zoomed in clip of the first one moving with the flow. Should I leave them be or are they gonna become something bad?

 

[lil sumpin]

Looks like a ball anemone

 

[exnisstech]

https://www.reef2reef.com/threads/what-is-that-a-r2r-guide-to-common-new-tank-hitchhikers.443382/