A bud-sport is a genetic mutation of any plant part (leaf, fruit, flower, shoot). Sports are clearly different from the 'parent plant', and can be asexually propagated to make clones, each with those very different characteristics.

What your situation sounds like, however, is that buds have developed below the graft. Fruit trees are grafted onto a different root stock. You need to remove those shoots and any others that may try to develop. They take energy and resources away from the desired pear variety.

I agree with rhizo. I am presuming you planted your tree at a depth that kept the bud union above the soil. Pear trees can be prolific producers of suckers from below the graft. To slow their return it helps if you can catch them while very small and remove them by pulling down sharply and tear them from the root. Cutting them off encourages more growth. Al