Without seeing pics, I'd guess one of those plants was stressed (easily done with autoflowers), and it grew sacs and tossed a little pollen around. I'd check the plant with seeds for pollen sacs above where the seeds are showing. It might be challenging to see if the bud has developed. If it's not that plant, check the ones next to it. I've had similar issues with autos, especially ones from breeders who aren't known for their top-tier autoflowers. The seeds might be viable, but you do run a risk since I believe they have a higher chance of being intersexed. However, plenty of great strains came about from this very thing happening.
If you can find the offending plant and pull it, then it might be worth it, but if you're near the end of flower and these seeds are just showing up, then there's a good chance it may not affect the bud too much.