It is possible they're just benign cysts...they often show up seemingly overnight, in weird places, including the neck/shoulder area. If there's no pain/they're not sore, they feel kinda squishy like they're little balls under the skin you can move & moosh around w/your finger, it's a maybe.
My dad had this one on the top of his shoulder, very close to the neck, that kept growing comically taller for a while...doctors didn't remove it for years cause it wasn't dangerous (they did eventually, cause it annoyed him when he wore shirts). I had a small one pop up on my wrist once, and years later it just disappeared on its own.
Anyway...obviously with the diabetes and just in general, get 'em checked out, but just saying...little lumps aren't always a sign of something to be worried about, beyond cosmetic concerns.
Luck.