When you take a kitchen knife and cut into a fruit, you are "cutting" (although realistically mostly crushing) the plant cells. However, even a sharp blade is only so sharp, and to extremely tiny things like atoms and molecules, the blade is extremely large and round and dull. So you cannot break bonds or chop up atoms with a knife.

In nuclear fuels or bombs the atoms are split when they are hit with fast-moving particles that are smaller than the atoms themselves (subatomic particles called neutrons).

The chemical bonds in molecules are too strong to cut with a knife. The forces holding atoms together are much, much stronger. Does that answer your question about why nothing explodes when we cut fruit?

You can see the cells in some fruit: they're hard, granular things because they have cell walls.

The way that a knife works is that it applies force over a very small area (the blade of the knife). This causes a tremendous pressure, which drives the matter on either side of the pressure point apart, thus cutting it. A knife cannot cut anything smaller than the blade of a knife.Since knives are made out of atoms, they can't cut atoms.

The splitting of atoms in atomic bombs happens as a result of a different process. Only some specific elements of atoms (and even then only specific isotopes) can do this, and it happens when they are struck by neutrons, which are particles smaller than an atom. However, even these atoms can't be cut with a knife, because the atoms are smaller than the knife is.