Is this a quite small ball python, as in an 07 hatchling or a bit bigger one? The smaller ones especially will jab at you with a closed mouth and will occasionally nip. Any snake can really. Think of it from the snake's point of view. It's small, it's in a pet store where people likely tap the glass, it's been handled by a lot of strangers, it's been transported to your home. It's hungry, not sure if someone wants to eat it and it just wants to survive. Wouldn't you strike out if you were in this set of circumstances and remember, it has a very basic reptilian brain unable to comprehend what is going on.

Let your snake settle in, make sure it's home is properly set up temps and humidity wise, make sure you are providing appropriate hides and in a week offer it a feeding. You do not have to remove it from it's enclosure to feed it. Feeding in the home enclosure will not promote biting (that's an old myth). Let it get a few weeks of feeds in it, then worry about handling once your snake is well-fed and had a chance to settle into it's new home.