It has characteristics that lead me to think it might be a dandelion, but the flower is too small (9mm), doesn't look like a dandelion flower (we have those in our front yard too) and they don't develop the fluffy seed pods. I've tried to add a picture of the plant itself but found it difficult to separate it from the lawn. So, I've tried to point out features. The long white line runs beside the stem. The oval inset is a magnified image of the foliage which I also added in a separate image.
The basal leaves look different than typical Hieracium basal rosette that can be seen on Internet images, so it may be not Hieracium after all. However, taking into account that there are 10,000+ recorded species and subspecies of Hieracium, I would not exclude the possibility that it is. For sure it is not Taraxacum (Dandelion) which flowers are borne singly on a hollow stem. What is also for sure, it is something in the Cichorieae tribe, to which both Hieracium and Taraxacum belong, as well.
