I have an offer for a job I am under qualified for. Do I take it?

I was laid off from a previous job where I had a few years experience as an HR Generalist for a couple years. While job searching, I found a job posting for a position where I would be performing similar tasks to my current role. In this role, I would be the only HR representative, replacing the current manager. When I applied, I was not aware of the stakes of the position, and that I would be the head of HR.

I do have a fewl years of HR experience, but because of my generalist position, I feel like I have not specialized enough in any particular area. I am well on my way to a degree, but I haven't earned it yet. I will point out that I was completely honest in the interview, but I can't help the feeling that I've gotten myself in too deep.

Is this just imposter syndrome or should I be concerned? Does anybody have experience running the entire department alone?