My vote is to not pull it now. After it has bloomed, you can always deadhead so that it doesn’t spread. I am curious to see the blooms.
Little yellow small sunflowers .they pop up here too and can seem to find the name.. could be mullein weed.
I also think it is a weed, but still the flowers could be nice. We have a weed here that looks very similar. They blow in on little structures that somewhat resemble dandelion parachute seeds.
The flowers are here, verdict says: Campanula. Nice big flowers and should have lots. A keeper and great for my street garden of natives to wild domestics (California poppy, foxgloves, native lupine and two varieties now of campanula)
Will be happy to scatter the seeds from this lucky surprise. Have several places I’d like to see this beauty.
Surprises like that beauty is good one. Usually most of my surprises are some type of noxious weed or banned plant.
The one bell flower has self seeded in the yard and will make a great companion plant to this new and larger variety. Looking forward to seed scattering. Creating beds now along the front fence.