Weird scab in nessarius snail

[coolbreeze]

Hi there - I’ve had this snail for about 2 weeks and just noticed this scab/lesion looking thing on his back (not the shell). Any idea what this is or if it’s a sign of something bad for my other fish?

 

[FernBluffReef]

Not a scab. Normal. When snail retracts it’s it’s cover

Called a operculum