Piercing..

Having your nose pierced can cause infection as you cannot disinfect inside.
If you get nostrils pierced there is a risk of getting a blood infection (cannot remember name) as there is a bacteria that lives in nose lining if it gets into blood stream makes you ill.
If you are getting septum pierced it can break which pushes it to side making nose breathing hard. If you get a piercing and it goes wrong being diabetic can make it harder to heal.

Once you have weighed up the pros and cons it is entirely your decision, I myself had a nose piercing for many years.
I also like the fake ones you can get now, no risk.

As long as you go to a proper studio to get it done and keep it clean you should have no problem.

I have had LOADS of piercings and they have all been perfect.

Nose piercings look good on cows, people not so much..lol

I have an urge to yank them out whenever I see people with them..

I had mine pierced but removed it now, I've also had septum and many other piercings all when my sugars was high just look after it and keep it clean and go to a proper piercing studio.