I didn't have a needle or something of the sort, I used a knife and pressed the tip of my finger agaist it and then swiped the knife away from me very fast without pressing on my finger.
This made a very small and controled cut that stopped bleeding very quickly, so it is possible to use a knife, but really if you have a needle use that.
If you aren't carefull you could end up chopping a piece of your finger off and well that wouldn't be pretty.
If you do go for it with a knife, use a sharp one and make a careful incision, not a huge adrenaline induced wild cut that ends you up with a huge scar on your hand and a new paint job for your house..
We aren't masochists or something.
Drawing more blood or making a bigger cut isn't going to show Satan you are more badass or dedicated either, it's just going to show you're a bit stupid really..
I hope you take this into consideration.
HAIL SATAN!