Skull-headed monsters have long been a part of things that go bump in the night, so it's not surprising they would find their way into the wildly popular niche of monster romance.
(Of particular note for this collection of titles: none of the skull-headed protagonists/love interests in this list are W--digos (rhymes with shmendigos), as using that term or the associated indigenous myth is generally considered culturally insensitive.)
Important notes: as an Amazon Associate, I may earn compensation from qualifying purchases through the links on this site. Some title(s) or author(s) may have been consciously omitted because they've used generative AI in their work, and/or exhibited concerning or unsafe ideas/behaviors. If a problematic author falls into those categories but still appears on the list below, please notify me, as I may not be aware!
The Duskwalker Brides Series by Opal Reyne - https://amzn.to/3URrKck
The Myths and Monsters Series by Beatrix Hollow - https://amzn.to/4fPIN6z
Beguiled by the Beastly Baron by YD La Mar - https://amzn.to/4i01Vku
The Prince of Broken Toys by Michelle Deimos - https://amzn.to/4hKNEI5
Primal Hunger by Harper A. Brooks and R.K. Pierce - https://amzn.to/4erByAJ