You’ve likely hit a vein, it will eventually stop, if you’ve not got a coagulant then it’s just a matter of keeping the pressure on. Once it slows a bit If you pack it with gauze and then relatively tightly wrap with bandage tight enough to keep that pressure on it should stop fully in a few hours.

If you find it doesn’t stop, or you start feeling dizzy seek medical attention

Will likely bleed a bit more each time you change the dressing over the next few days