Guest post not indexed? You sure its of good quality?
Manual social media submissions will do the stuff... if you have access to the property in search console, you can ask to re-crawl it.
ping from some pinging website and also share some on social ,these days google slowly indexed backlinks but by using these 2 scenarios i did many
I can't share a guest post on my own social media can i?
It has to be the social media that is linked to the guest post website.
How are you checking if it's indexed? It should be indexed by now if the website is of high-quality. Did you check for noindex tags(I doubt that's the problem but still)?
If you are sure the website is of good quality then you should wait, no need to rush it, it will index by itself. Or send some social signals and weak links.