Give it a day or two to see if it goes away. Can't say for sure without a zoomed in pic, but it look like a little big of Mesenterial filament that is sticking out. They're the filaments lobos, scolymia, favias, and some other corals use to attack other competitor corals that are nearby.
From time to time a see a little stick out of mine like that even if there are no other corals nearby. Usually gone (e.g. retracted back inside) within a few hours to a day or two.
The real so takes place when it launches an all out attack on a nearby coral. If I have time tomorrow, I'll post a pic of that. Every month or so, mine sends out a web of mesenterials onto some nearby palys -- which are unaffected by it -- in a vain effort to try and destroy them.
