I am a PhD student and I wrote a journal paper recently on a topic. The methodology and the results are completely my own. The idea is also my own.
The way I build my measurements are based on a research I carried out with a master's student during his master's thesis. However, later developments and everything is mine.
When I submitted it, I acknowledged him and gave credit to his thesis. My supervisors are always there as authors anyway. However, for some reason, I feel bad emotionally because I didn't add my student as an author. When I submitted it, I thought very logically when I wrote all the author names and the student hasn't done any further development or editing in this paper. So, I didn't add him as an author.
I also informally informed him about the acknowledgment and he seemed okay with that. Later, however, he asked me if we could write more papers together and I really liked that idea.
During this process, I felt probably he didn't like that I didn't include him in this one. I've communicated transparently why I did what I did (even without him asking).
I don't want to make our professional relationship worse. So, I told him that I don't know what's right and ethical in this case and I would discuss it with my professors, based on the outcome I can change the author's names after I get the first revision.
What should be my approach based on your experiences?