Re that mark on Mora's/Lugosi's right temple...

Several sources, including critic Mark Viera and Turner Classic Movies writer Jeff Stafford, have claimed that MGM cut out suggestions of incest between Count Mora (played by Lugosi) and his daughter Luna. Viera further claims that the original screenplay explained that Count Mora was condemned to eternity as a vampire for this crime and shot himself out of guilt (which explains the otherwise unaccountable spot of blood which appears on Lugosi's right temple during the film). This was an unacceptable topic according to the standards of the Production Code, and consequently cut from the film. While the subplot was cut, the blood spot on Count Mora's face remains in the finished film and is never explained.

https://en.wikipedia.org/wiki/Mark_of_the_Vampire#Alternate_versions