I am type two diabetic and started insulin 3 weeks ago. i have had genital itching and swelling since. should i be concerned?

Likely not: If you needed to have Insulin started recently i would suspect your blood sugars have been a little challenging lately. If that is a true statement then uncontrolled bs's could lead to glucose in the urine which puts you at risk for yeast infections. Also your immune system is adversely effected which leads to other infections.

Probably unrelated: While diabetes can affect your immunity, it's unlikely that Insulin caused your symptoms. Still, because you're at increased risk for infection, go see your doctor for an evaluation & treatment if necessary.