Identifying Weed in Yard

This weed appears to be in a violet. You say it has not flowered but is it in an area where you mow? If so, then you are probably mowing off the flower and seed heads. At any rate, this is thick rhizome (root) structure, hand pulling or digging is not effective for control. I am providing a link below to a Penn State article that will give you an overview of the life cycle as well as a list of herbicides with active ingredients that have proved effective with violet control. Note that repeat applications may be necessary over the course of a growing season. Hope that helps and good luck! https://extension.psu.edu/lawn-and-turfgrass-weeds-wild-violet