Awfully small photo. It does remind me of Rose Campion, which is a biennial...it grows foliage the first year and flowers the second(it looks like it's sending up flower stalks), then produces seed and dies. The following year the seeds it dropped will produce the foliage rosettes, and so on and so on...
I'd give it a bit more time and/or plant it in the ground.

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Hope this helps, and hope the plant does turn out to be the Rose Campion(Lychnis coronaria).

If this is a plant that you do not want growing where you do not want it to grow it is a "weed".
If this is a plant you think you might want but it is growing where you do not want it to grow, you can move it and it is not a "weed".
The photo is too small to identify the plant.