It reminds me a lot of a weeed I sometimes find around here and I quickly pull it out before it produces blooms and seeds.
It could be something else, but I doubt it.
Mine also grow rather tall, and they have snappy hollow stems.
if no-one can help with an ID, you could let it bloom and then we can figure out. Can you take a pic with the "TOP" ? Maybe there's something already going on there.
