My first brew had that because while racking to the bottling bucket I sucked up a bit of the yeast cake. Every one of my bottles has a fine layer of yeast at the bottom, still tastes fine.
Yep, sounds like you sucked up some sediment or still had yeast dropping when you bottled.
I'll let my beer drop completely clear in the primary before bottling. It takes weeks before it's carbonated but it leaves just a fine dusting in the bottom of the bottle.