Weed / Perennial in new Lawn

My lawn got seeded last September but towards November this weed started to feature and has spread pretty rapidly across the garden. I have used some apps to try and identify it which some have said poppy or groundsel. Any ideas or thoughts across the forum if anyone has seen these and if so ways to manage / treat them? I have included some images.

 

Looks to me to be similar to groundsel alright. It should be killed off by regular mowing once your lawn grass is mature enough and the ground is dry enough to mow your lawn regularly. Grass grows from the base of the plant so mowing is more like just giving it a hair cut while plants like groundsel have there growing point higher up and this is chopped off by mowing and so mowing is much more damaging to them. If it was a small area of lawn you could also simply use something like a trowel to loosen the soil around the roots as you pull the weed plant out of the ground while trying to avoid digging up your grass too much. There are also selective weed killers for lawns but I prefer not to use chemicals in my own garden as it makes me feel more comfortable to spend time in a garden that is chemical free.

Happy gardening!