It's a viola (violet) species. Should be producing tiny purple flowers shortly and if allowed to go to seed, they will spread widely throughout the lawn.

Any broadleaf lawn weed killer should work but check the label to confirm violets/violas are listed. A spray formulation is a better approach than granular - faster, more efficient and less likely to leach into groundwater and add to pollution. Bayer makes an excellent product that can be used as a handheld RTU, a hose end sprayer or a concentrate to mixed and sprayed. Bayer All-in-One Lawn Weed Killer

Thank you so much!!