From the picture I would say those are adventitious roots that started to grow farther up the trunk, possibly because it was planted too deep at the nursery. I would cut those off so they don’t have the opportunity to girdle the trunk and cut off valuable nutrients from traveling through the tree’s vascular system. 

If that lean were in a house or garden plant I would suggest watering. Obviously, that’s not the case here. This is an educated guess because the leaves are so small in the picture but the canopy makes it look like a river birch or a relative. The trunk does seem thin for the  canopy and so might have bent under the weight of the leaves. You know what kind of tree it is.

I suggest you consult a certified arborist to diagnose the problem. I suggest you do that so you have an expert to help you stake and  straighten the tree until it can stand on its own.