Congrats and yes the advice to write the next book is sound advice but you can do some small promotions for this book to get it in front of a few romance readers.

Is it in enrolled in KU or are you going wide?

If it's in KU try a 3-5 day free or $0.99 promo. Or do a kindle countdown. If it's wide try a 0.99 short promo. Use some inexpensive promo sites like these:

costs $7 = Sweetfreebooks - your book can go in the new category if you have no reviews. Just a heads up, No erotica in new category.

costs $5-$20= Bknights (Bknights is more effective for free promos)

free to advertise = awesomegang

There are dozens of free $0.00 promo sites too

.Get a mailing list link in your book and when your next books nearly done, ask your subscribers if they want to be one of your arc team members. Build a little team of arc readers and a street team who will help you promote your books on social media

Things that might work or might not work and can take a little time away from writing. Some on here are going to disagree with some of the things I mention below but I spoke to an author who's doing this now and she's seeing a small uptake in follows and sales:

.Use your twitter or facebook account to add little snippets from your book. That takes 10-15 minutes to do

.Cast your characters. Add a few pics of famous people that look like your characters

.Tell your followers about another author you like who writes in your sub-genre and give them a little promo push. I've seen one new author become friends with a bestselling author by doing this. You could also decide to do a box set later with a couple authors you promote and make friends with on social media.

.Once your next books finished, think about putting a small sample on your website. You could do what Christina Lauren do, they tell their mailing list subscribers they can read the first chapter of their books before it's even released. They link it to their blog.

I removed the links because my comment wouldn't post