Crystallization is a normal physical change in honey. It does not, by itself, mean a jar has spoiled. The rate and texture vary with composition, temperature, and storage.
Use the texture
Crystallized honey can be excellent on toast, fruit, oatmeal, or in baking. A fine crystal can make a jar naturally spreadable.
Warm it gently
If a liquid texture is preferred, place the closed jar in warm—not boiling—water and stir gently.
Store it simply
Keep honey closed and dry. Avoid introducing water or food into the jar, and treat its changing texture as part of the material.