There's a big difference between the maples. Out west they have big leaf, which is soft. Then they have canyon maple, big tooth maple, and rocky mountain maple, all of which are hard maples. In the east the hard maples consist of numerous sub-species of sugar maple, which are hard, and some soft maples like red & silver. Maple of some variety grows in pretty much every continental state, and all can have burls.
The question is which type of tree you have, and what type of burl does it have? Some burls will be nothing but a bulbous growth, no extraordinary grain to speak of. Some will have densely arranged knots(eyes). Others will have wrinkled up, bubbly grain. A burl can have a variety of any or all of these features, plus have colors from an entire spectrum. I'd assume you live in Kentucky, and since the tree is in your yard I would guess it's sugar, red, or silver. A picture of the tree and a clear picture of the burl, with description of size, would help a lot in determining whether it's worth looking into or best to just leave it be. Since it's in your yard, it's probably best off where it's at.
