WIBTAH if I renege on my offer to swap shifts with my coworker?

Coworker asked me to swap night shifts (we all have to do one night shift per week). I initially said no because that night shift was only two days after my regular night shift, and I didn't want two night shifts with only one day's break in between. Yes this would mean that I wouldn't have to do any night shifts next week, but I'd rather do one shift per week, instead of two in one week and none the next week.

There were a few other people on the team he should have asked first (people whose shifts are further away, so the swap wouldn't have been as difficult on them). He claimed that he already asked them and they said no.

I also just did not want to help this guy period. He has repeatedly agreed to do work then pushed it on me at the last minute. He's tried to take credit for my work. He's needy, whiny, clingy, and undependable.

I was going to tell him too bad, I can't help you. But then I realized that my boss would probably just make me swap anyway - we absolutely need to have someone cover the night shift each day. And if my asshole coworker couldn't cover his shift, then the boss would make somebody else do it. I figured either I agree to swap now, or the boss comes along and makes me swap anyway.

But after thinking about it for a few days, I think I should have stuck my ground. I shouldn't have conceded so easily, I should have made our boss get involved and ask me to swap.

I'm considering reneging and saying "Actually I can't cover your shift, find someone else to do it", just so I can stop feeling so angry at myself. My reasoning will be "it was originally your shift, so finding a replacement is your responsibility." But I'm pretty sure I'll be considered the unreasonable one in this case. WIBTAH?