Ah, then it might not be a big issue

How is it doing today???
They will sometimes make that big bloated looking foot, either to move around or to get a better grip on things.
I suggest that you keep a really close eye on the tear. Nems does not have a central nervous system, so it cannot receive a damage that it cannot recover from.
Anemones can practically re-grow out of a left over tissue of anemone
The main concern would be, that when an anemone tears, it can begin to decompose.
So I would presume that your Nem have only smaller power reserves and since it had new lighting, it reacted by trying to find the optimal position. That was possibly too hard for it and it ran out of energy during the night (they kinda relax during nighttime, they also use that laxness to move around during nighttime).
If the Nem can close the tear back up, as many of us have seen happen after power head accidents, it can easily recover.
If you notice the Nem tearing more and more, it means the Nem have begun to rot and then it becomes to risky to keep it in a tank with other livestock.