Pruning Maple Tree

So, a maple tree has started growing itself in a spot where I already wanted to grow another tree; I like maples, it somehow seeded itself despite there being no maple trees anywhere closeby, so I'm letting it grow.

Now, the tree presently looks like a ~8' tall stick with leaves all over it (flash is jacked on my phone, so I can't take a pic now). When I go to a nursery, the trees that are approximately this tall look a lot more "tree-like", as in the trunk has no leaves for the bottom 4', and the top is a "ball" shape. I fear, without pruning, that my tree will be a 15ft tall stick, and look a bit silly, before it starts filling out, but maybe this is how it's supposed to be ... I don't actually recall seeing any standard maples @ the nursery, now that I think about it.

Googling seems to show how to prune a tree that looks a lot like a tree, but needs to be groomed for whatever reason (this I know how to do), not how to make a tree fill out when it looks like a leafy stick. Should I be doing something, or just let it be?

Edit: My tree looks something like this (not my tree, this is from Google), but imagine the "body" part being like 1/3 the diameter ... if not smaller.