Stale food itself won't make you sick.
But if the stale food has started smelling bad, has mold growth on it or you think it may have bacteria in the stale food then throw it out.
Usually you won't get sick from eating stale food but you might get a stomach ache.
If the stale food tastes really bad has a bad smell to it or you just don't think it's any good then throw it out and don't risk your health.
I've eaten foods that have gone stale such as chips, bread, pretzels.
But some stale foods I just cannot get down as they taste off.