Thanks for posting your query.
Although chewing raw rice doesn't make any harm but still this is not a good habit.
You should consult with internal medicine specialist/ psychiatrist
This is a sort of neurotic disease
This can be treated by medical and non-medical therapy.
Non medical therapy includes behavioral therapy
such as diversion of mind and involvement in some other task when you have increased urge for eating raw rice.
Medical therapy includes use of selective serotonin reuptake inhibitors and tricyclic antidepressants.
DR. Mayank Bhargava