Found a trick for blood as I had a nose bleed on my pillowcase a month ago. This method worked so well I couldn't believe it.

Soak the spot in some hydrogen peroxide as others have said, maybe 20-30 minutes. Squeeze out any excess so it is not dripping. Then using a clothes iron and hot iron over the stain for about 20 seconds or so and then repeat the process with the hydrogen peroxide and hot iron again a few times until the stain is completely gone or just has an ever so slightly faint outline of what it once was.

Then once gone, give it a light wash in the machine as normal.