Season chicken on both sides with salt, pepper, and cumin. Heat oil in a large skillet over medium high heat. Cook chicken until browned on one side, about 3 to 4 minutes. Turn chicken and cook an additional 3 to 4 minutes until done. Transfer to a plate and set aside.
Add lime juice to pan and continue to cook, while stirring, another 2 to 3 minutes until slightly reduced. Remove from heat and add sour cream, cilantro, cayenne, and lime zest. Serve chicken with a dollop of the sauce over top.