I have some scrathes/abrasion that does not heal fast and turned blaken/darker wholes. what should i take/do to heal it?or symptom of diabetes.

Pigmentation.: You are describing post-inflammatory hyperpigmentation which is a condition whereby the skin darkens after trauma or other inflammatory processes. It is very unlikely that you have diabetes due to your age (type ii diabetes usually hits later) but have a physician perform an exam due to your obesity and increased thirst. Also, keep sunscreen spf 30 or higher on the dark marks to fade them.