Make sure the new queen has plenty of open space to lay in. And keep your fingers crossed. One of those should help.
I hate to say it but if it swarmed two days before you split then there weren't any eggs to make a queen for the split. So now it might be wise to have at least one queen cell in each half of the split. That means you have to go in both of them.(actually there are 2 because I split it 50/50 2 days before it swarmed)