Never had one, but I find having my blood pressure taken can be uncomfortable, couldn't imagine having to put up with it every half an hour!
I bet you'll be glad when it's over.
It's normal of it hurts a bit, makes your hand and arm numb, I know I can be rather prone to mild cramping as well
Don't worry it's no where near tight enough to cut off blood flow even though it feels tight , but it can press on the nerves giving you numbness .
They are fitted with a censor so it won't ever over inflate.

It's a good test, as often your anxiety can be higher when your own doctor checks your blood pressure.
I hope you can get some sleep x