When there is a noun or a pronoun with a participle -- -ing or -ed form-- after it, it is
called a nominative absolute.
...That being said, we will go forward from here.
...The project completed, we went out to celebrate.
These take a comma wherever they are in a sentence.
...I will have to drop my argument, that being true.
...He had to have surgery, the leg being badly injured, on that same day.
Happy punctuating!
Margie