Honey, it doesn't seem right to me that you're going to be punished for something that's outwith your control. I can't remember the last time I came using my fingers - not when there's batteries and nipple clamps in the world. Maybe desperation will provide that extra push you need, but I doubt it. You say you're new to this and I suspect your Master is too. He should really be training you to come like this over time, not threatening you with punishment when you fail to achieve the impossible. Punishment is for wilfull disobedience or poor, undesirable behaviour, not really for this sort of thing.
Give it a good go, and tell him how hard you tried, but really, you both need to talk about this as you seem to be at cross purposes. He should understand the difference between good intentions and (untrained) impossibilities, and you should appreciate that you have a positive right to be led in a way that's fulfilling for you.

The best of luck, but you really shouldn't be panicking over this, just preparing to have a good talk with your reasonable, I hope, Master.

Pearlgem x x