What do you do when you've interviewed for a position at a company, then later the day find a better job posting at the same company?

I interviewed for a CNA position at an in home care company and was given a conditional offer (once my record comes back clean I'm hired) however at the end of the interview I was given the real deal which is that the pay and the hours are really terrible. My plan was to call back and say I'd been given a better offer and decline however I found a posting for an HR position with the same company that pays a lot more, better hours and I'm 100% qualified. How bad is it to call back and withdraw my application for a care giver and resubmit it for the HR position? Is it even worth pursuing?

(Interview went very well, I have great references, work history, clean record etc.)

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