I decided not to apply for a job, but two people filled out reference forms for me already, what do I do?

Hello, I was applying for a position as an orientation leader at my school, but I discovered that the position is going to conflict with 2 summer course I NEED to take. I feel really bad because I know the two people I asked already completed the form, and now this was a complete waste of their time. However, the form was very "low-key" as in it didn't require a letter of recommendation. It was just a form and it asked the person recommending me to write a few sentences of why I would be good for the job. Regardless, I still feel bad and I know I should tell them that I decided not to apply since they will be eventually asking me if I got the job.

What should I say to them? One is my current boss and I think she will understand completely, but the other is a professor and I don't want to piss her off lol