I think its the weed Tufted Vetch? Its a member of the Pea family. You need to dig it out as its roots spread.

I quite like vetch as it is a native wildflower and it is a vital source of pollen and nectar for bees.

True it does have creeping roots like bindweed so maybe not the kind of thing to let have free rein in the garden but if you have a wild part of your garden ( like behind a shed ) maybe let it fight it out with the nettles then the bees can still have place to drop into for some nectar.

Thanks