Knitting in the round after tubular cast on

I am knitting a hat which requires casting on with waste yarn. I need to join since I am knitting in the round. The first color needs to be added to start the first row. My question is: how do I close the gap in the needles since I am not joining with the waste yarn? Adding the first color does not join needle three with needle one. I can’t tie the two yarns together so that I can pull the needles together since I have to remove the waste yarn later.

I would wait and let the needles join at the next round. You can stitch up any gap with the tail later on.