Quick take
If both hot and cold well water smell, test for hydrogen sulfide and related iron/manganese. Whole-house oxidation/filtration is a common treatment path.
Check hot vs cold first
Hot-water-only odor can point to the water heater, while odor in both hot and cold water is more consistent with the source or plumbing.
Whole-house sulfur treatment
Air oxidation and regenerating media are commonly used when hydrogen sulfide is present in source water.
Carbon alone may be insufficient
Carbon can polish odor but can be overwhelmed when sulfur loading is significant.