If you have room, transplant it and observe it for a while. Might be the next big thing! ...especially if seed came from one of the more diminuitive cultivars like Teddy Bear or Little Gem.

My neighbor has a pin oak but I don't think it's mature enough to produce acorns, I've never seen acorns anywhere in the neighborhood. I have what is possibly quercus nigra growing up through another tree on my property. Sadly I live in a typical NC development which is mostly crepe myrtle, pines, and maples. I would love to keep these guys going, although I gather that if they are water oak they're not desirable. One of them is in the middle of the "lawn" (bermuda). If I fence it off will it have a fighting chance or will the bermuda eventually choke it out?

Compare with L. japonicum.

Yes, the right one looks like sweet William, Dianthus barbatus, and the one on the left snow in summer, Cerastium.