Hello,
I have gone through your query and understand your concern.
I suspect you might be suffering from 
Diabetic neuropathy. That is why you have 
numbness in fingers.
Yes. As you afraid of, you may develop 
erectile dysfunction if you do not control you blood sugar with in normal limits.
If you control your blood sugar, that protects nerves throughout the body and also the nerves responsible for erection.
Your doctor prescribed Oral Hypoglycemics for you.
It is usual and with these the sugar can be brought in control if you take the tablets regularly.
Additionally, you have to be on Strict diabetic diet as prescribed by your doctor. 
Exercise regularly for at least 45 minutes a day. This will help in improving your circulation.
Have regular check on blood sugar and 
HbA1C every 3 months and review with your treating physician.
Hope this helps.
Please write back for further queries.
Wishing you good health.