Otherwise known as Morton’s neuroma, a nerve in the foot becomes irritated and thickened, which can cause severe pain, burning, numbness and tingling. The condition typically occurs in only one foot but can affect both feet. It usually affects the nerve between the third and fourth toes, but sometimes the second and third toes are affected. The exact cause of this condition is not known but may develop from chronic stress and irritation of the nerves running between the metatarsals and is linked to flat feet.