Black bit in olive oil
As per your additional comment it's very probably a slice of olive skin and as high-quality olives are preserved in virgin olive oil, this will most likely not make any difference to the food safety nor taste of your product.

Having said that, without a biochemical analysis of the speck we cannot be 100% sure and it could be a speck of Black Nightshade, but the odds against that are enormous.

Though not zero...