crabgrass?

That does look like crabgrass. I pull mine out by hand when it is the size in the picture before it grows deeper roots. You should put down crabgrass in early spring to prevent it before it emerges.

You can still hand-pull that, but if it's spottily in other parts of the lawn as well, I might suggest spot-spraying with Weed B Gon Crabgrass Killer. Mix up the concentrate in a one-gallon sprayer (it's cheaper that way) and keep after it to avoid having the CG seed out.