Is this a sapling or a weed?
It may be fair to say this plant is a weedy sapling. It does look like a tree or large shrub. My first guess is Sambucus (elderberry). Does the foliage have a strong odor when crushed? There are nut trees also with similar leaves.
When it gets large and flowers or fruits, you will know what it is. My suggestion is to remove it and either repot to grow it on to identify it, or just remove it because it is in the wrong location for a large tree or shrub.