This effect is actually a pretty quick and easy EffectsLab DIY effect. Here's a little tutorial I whipped up.
1. Here's my original picture of footage of the scene I want to add the effect to.
2. Make a new mask around the inside of your footage or picture with about an inch of space for feathering between the mask and edge of your video. Now set the feather to 125 and the transparency to 75 and invert the mask shape by clicking the red dot icon [
: ] so it turns green [
Mask feather settings:
3. Open the canvas color box by clicking the little box icon (black by default) just under the H of the 'Help' tab at the top of your screen and set it to the below settings then click OK.
4. And this is what the final effect should look like:
If you are working with video and want the effect to appear at a certain time you can go to the first frame of your video and set the mask's transparency to 0 then go to the frame you want the effect to begin to appear and set the mask's transparency to 0 again, jump 1 frame forward and set transparency to 25, then jump 1 frame forward and set transparency to 50, then jump 1 more frame forward and set the transparency to 75. When you want the effect to disappear, go to the frame you want it to begin disappearing and keyframe the mask's transparency at 75 then go to the frame you want the effect to be completely gone and set the transparency to 0.
You can also touch up the effect a bit by adding a little artificial camera shake and blur when the injury occurs and slowly fades away over time, but that's optional. Overall I think its pretty close to the CoD4 injury effect you're shooting for.