Step 1
Lets open up any picture you would like.  In this case we have chosen Mondala.

Step 2
 Open your layers palette from Window > Layers and create a second layer. Use your Lasso tool and make an outline of where you want the blood to be as displayed on your subject. 

Step 3
Should look something like this.

Step 4
Fill the area selected with the lasso in a dark red color and select the layer as Color Burn on your layers palette. Deselect the selected area if you haven't done so yet.

Step 5
Now head over to your Tool bar and pick the smudge tool. Be sure the brush size for it is rather small.

Step 6
With the smudge tool, smudge the blood down until it looks more realistic.

Step 7
Select the Burn tool, located to the right of the smudge tool on your Tool bar.

Step 8
With the burn tool, deepen the blood wound by making it darker on the center spots which should be the middle of the wound.

Step 9
Now, go to Filter > Texture > Texturizer. Once the box opens up, select Burlap for your Texture. Scale it to 200%. Give it a Relief of 2 or 3. Now press OK and presto!

Step 10
Your Completed Project.  Nice Scar Mondala!