He named our son Three!

Everyone in the hospital looked so puzzled at the name. Of course I didn’t want this name. He didn’t incorporate the name I wanted at all. What should i do? The lady said she will hold off sending it in to give me time to change it but if I do the affidavit of parentage that he signed would be voided. So if I change it I would have to leave his last name off. We are not married and we broke up a few months ago. I didn’t mind him naming our son but a number as a name is absurd!!