I'm not sure Nova Launcher is even available in Huawei's AppGallery. You'd have to download the apk installation file from the internet (I recommend APKMirror as a safer source of apk files) and install it manually.
To access Nova Launcher's paid features on a phone without the Play Store could prove to be tricky. I suppose you bought the Nova Launcher Prime app that acts as a licence for the main Nova Launcher app's paid features. One way that may work is if you'd download the Nova Launcher Prime app you previously bought to a phone with the Play Store, backup the apk file, transfer it to your new Huawei phone without the Play Store, and install it.
Be cautious though: some paid apps check if you actually bought the app in the Play Store. This check may fail if the Play Store isn't present. If the Nova Launcher Prime app implements such a check, you will not be able to use Nova Launcher's paid features on a phone without the Play Store, even though you bought it.