What Causes Prolonged Healing Of Blister On Hand When Suffering From Diabetes?

To start with I have diabetes. I recently had a scratch on my hand so i cleaned it put neosporin on it with a band aid I woke up with blister like spots on my hand where the scratch was. and also on my other hand my thumb started to crack and peel and it has peeled way back the end of my thumb and i have been keeping it clean and bandage it with gause and neo with no results it does not seem to be heeling what am i doing wrong?????? Please help......