Doesn't look like nettle to me, at least not Urtica dioica. Nettle flowers don't shoot up above the plant like that, they are clustered among the leaves up and down the stem.
Let's see if I can put an image in from the 'net:
Hope that works...also, the leaves on that plant look more elongated than nettle, and not as deeply toothed, though I'm sure there are variations amongst nettle plants...
Thanks Jessica and Mitch. Mitch you were spot on as being white vervain after reviewing pics and info online about it. May I asked how did you indicate that?