AFAIU bluehost does not support the acme protocol, so you’ll either have to manage your certificate manually or (recommended!) move to a different dns registrar.

If you are wondering which provider you should switch to, basically all the serious ones will work… IDK if this is relevant for nginx, but here’s a list of the supported ones for the client I use go-acme.github.io/lego/dns/

If you are unsure and want to experiment before touching your current setup, you could register a new cheap domain (less than 1$, see tld-list.com), use it for your tests, and then not renew it.