You might benefit from using a cloth or paper towel to remove  excess blood. Don't rub the stain, as this can spread the blood stain or push it deeper into your upholstery. Use a dabbing motion to try and remove as much of the blood as you can, changing the cloth/paper towel when needed. Mix 2 teaspoons of salt with 1 cup of cold water and pour the solution into a spray bottle. Hot or even warm water can set the blood stain permanently to your car upholstery, so be sure to use cool water when applying the solution to your stain. If you don't have a spray bottle, dip a clean, white cloth in the saltwater solution and blot the affected area, changing your cloth as necessary. If you are working on a large stain, start on the edges and work your way towards the center; this will keep the stain from spreading. Repeat spraying and blotting until the blood stain is gone or the cloth is not absorbing any more blood. Use a cloth dampened with cold water, rinse the remaining solution from the spot. Try not to scrub at the spot; dabbing motions will draw out the excess solution most effectively. Using a dry cloth or paper towel, dry the area by gently pressing it to the stained area. If the stain is still visible, you may have a permanent stain, but a stronger method might also solve your problem.

Summary:
Blot the stained area. Prepare a saltwater solution. Spray the saltwater solution on the stained area. Blot the area with a dry cloth to absorb the excess solution. Rinse your blood stain thoroughly. Dry the area.