This is due to food impaction problem. Please stop using tooth pick or pin. Instead use interdental brushes and dental floss. The smelly substance is your food particles accumulated there. The smell develops when it get accumulated there for more than 6 hours. Please visit dentist, go for professional cleaning and then take an IOPA to rule out dental caries( tooth decay) or periodontal issues( gum problem). Depending upon the result go for the treatment.Address the problem at earliest to avoid severe damage to your tooth and gums. Hope this helps you sir.

Stop using nails and tooth picks firstly Visit your dentist go for scaling Gargle with warm water after every meal

Go for scaling and polishing Brush your teeth twice daily Do gargles with betadine gargles