Flowers and Plants: a request for help

I have this tree which grew randomly in my back yard, and i intend to keep it, because it provides shade in the heat of summer. I am, however, puzzled. It has the general appearance and size of, perhaps, some kind of fruit tree. It has never borne any fruit but its still young. Also, it sprang up with multiple trunks and I am therefore considering the possibility of apple, as I vaguely recall dumping a core into the yard at some point a few years back. Anyway, here’s a photo of the blossom, if there are any horticulturists amongst my visitors, I would appreciate a comment and suggestion regarding the plant, and what it might possibly be.