Do not waste it. Pump it to relieve your pain and save it for a day or two in the 'fridge. You will find that your production is very close to the demand of your child.
It is good that you are productive. Many women do not have the choice to feed their young naturally.
And, you will have days like that ahead of you, every time your baby will need more than he did before. It will take a few days of him wanting more than you have, that will make you produce more than he needs for a day, and then it is getting to just the amount he needs that time.
It's amazing how well demand and supply adapt so easily. Even the type of milk you make will adapt to his needs. What you have extra now, you can freeze, but, it is what a baby of a few weeks needs. Not what a baby of a couple of months needs. So, freeze it, for that day where you may have a cold and produce less than he needs. But don't keep it for too long.