Ficaria verna.

Thank you. That's it. should i let it grow as it is in a shady area and perhaps could be good groundcover.

but is it invasive on lawns?

thanks again. I am in CT and hadnt seen this before

It's pretty invasive just about anywhere.....can certainly invade lawns if allowed to spread. And comes and goes rather quickly in spring so easily missed for removal.

It will invade anywhere there is moisture, by seed, by tubers and by bulbils which grow in the leaf axils. Don't pull it, dig it. And try to get every morsel of tuber. I gave up long ago in my garden but it is native here, not an invasive species, so I can live with it.