Hi,
Thats the shell still attached for sure, some plants do this as I had it happen once or twice. If you can gently encourage it to come of by spraying the slightest bit of water on it, to wet it, you can gently try tweezer it off. But you can always give it another day and see if it falls off by itself. I'd still just drop a splash of water on it to soften it up. Hope this helps.