"
[Niall]
I've tried to ask myself
Should I see someone else?
I wish I knew the answer
[Harry]
But I know, if I go now, if I leave
I'm on my own tonight
I'll never know the answer
He knows that she is the one he's been looking for. So he doesn't want to be alone that night. If he is alone without her, he will never come up with the answer.