The picture does not look like gangrene. This is most likely an athlete's foot infection
What is athletes foot?
A common fungal infection affecting the skin of the feet is called athlete's foot, or tinea pedis. This kind of dermatophyte infection is mostly brought on by fungi that are members of the Trichophyton genus.
Extremely contagious, athlete's foot is frequently spread in warm, wet areas like swimming pools, showers, and locker rooms. Athlete's foot is generally a mild condition, but if left untreated, it can lead to more severe infections and complications.