It looks like your tree has some sunscald. Not much you can do about it now, but wrapping the tree trunk in winter can help prevent it. It looks like it is healing nicely, though.
To strengthen the tree, I would remove the stakes. Young trees are actually better off without them, and if they are really needed, shouldn't be used after they're in the ground for a year (you can shake the tree at the base to make sure it has rooted). You want the tree to develop resistance to the wind, and a flared trunk at the bottom, which occurs as the tree is forced to build tissue to respond to wind forces. My guess is that taking off the stakes will also strengthen the tree near the scar that is forming. It might be the case that the tree will break if the scar is deep enough, but there's not much you could do about that anyway.