Its bat poop, don't worry, it usually doesn't make any harm and it will fall off with the wind or with a little shake at harvest. Usual thing to happen outdoors.
Usually they fall on the soil under the plant and serve as fertilizer, but if they stay on the plant it may trigger the plant to produce more thc as a form of chemical wars, thc vs bat poop, who will destroy who... i had to take about a thousand of those in outdoor crops while trimming.
So worry not m8, but it wont hurt to take them out as they appear.
Gl growmie