I believe I've had something similar. Never caused any problems. Just keep your eye on it. Good thing about slow poke Nudibranchs is they are easily picked off anything they are bothering and Wrasse like to eat the babies if eggs were laid. Ya, I know, I'm kinda laid back about it.
Aloha,
Mark
Edited by Mark Peterson - December 24 2013 at 6:34pm