Hello sir.
Since you are a diabetic patient, it is a "must" to maintain your oral hygiene, and get a regular clean up done, because
diabetes increases the risk of gum diseases, and it may further lead to heart problems (scientifically proven).
You also need to get rid of your tobacco chewing habit, as it will not only stain your teeth, but can also lead to oral cancer and other systemic diseases. And since you are diabetic also, these things will add up and worsen your systemic health.
Next Steps
go to your nearest dentist, and get a thorough clinical examination done, and get your teeth cleaned.
Health Tips
once you get your teeth cleaned, then just maintain your oral hygiene, and say no to tobacco.