I don't think you have any problem. This has happened to me a few times and with poly seeds, sometimes it splits and I plant them all and some still germinate.
At the worst you've cut off some of the food for the emerging shoot while it relies on the stone. It may just have to get big boy roots and feed itself sooner
By the way, if Pickering is Polyembryonic which it well may be, you may have a few more sprouts still. .. and all you may have done is knock off one of several potential sprouts.