As the self-publisher of your novel, you get to the make this choice. I’d urge you to enlist the help of someone with experience. That may be an editor, or it may be a fellow trusted writer, or someone else entirely. Here’s why: Feedback is crucial. It allows you to see your work from a fresh perspective. Writing is such a solitary effort. To do the work, you have to spend quite a bit of alone time with the page. It’s easy to find security in that. Still, this creates a “safe” space, where the only criticism is that which you’re willing and able to give yourself. These are the very limitations that make it hard to see what others might have to offer.
Bringing in other readers can expand your understanding of what you’ve managed to do and where you may have fallen short. This will not compromise your control over the work. All comments and edits that you receive are simply suggestions. You don’t have to implement any of the changes. However, you’ll serve your novel well if you choose your readers carefully and consider all feedback with an open mind.
If you’ve never shown your work to anyone, you might start with a trusted reader or a writers’ group. An editor might be more useful later in the process, when you’ve had a chance to take the novel through revisions. You may even have a better sense of what you want from an editor at that point, too, and can embark on that process with more focus and confidence.