My dad has numbness in one feet n sometimes no feeling even of wearing shoes or not.why?

Neuropathy: Numbness in feet is some sort if problem with the nerves. The most common cause is neuropathy, from diabetes or some other metabolic condition. Nerve impingement from a bulging disc or the like is also possible. A podiatrist should check your father's feet for local issues, but will likely want to get nerve conduction studies or refer to a neurologist for a complete evaluation.

Numbness: This may well be diabetes but there are other causes. Seek the help of a podiatrist for an evaluation