I guess a lot depends on what you want to argue after having read this short story. I suppose the central image is the "worn path" of the title, which Phoenix Jackson treads every year for love of her grandson. What you could focus on is how this story presents us with an archetypal journey where the protagonist has to face several challenges in order to be successful in her quest, that is all based on love. Thus you might use the following thesis statement:
"A Worn Path" presents us with an archetypal journey where the protagonist sets out on her quest for love.
This would allow you to examine the archetypal elements of the story and the nature of the challenges that Phoenix Jackson has to endure. Good luck!