Wheatgrass is a powerful hemostatic agent i.e. it helps stop bleeding from open wounds, deep-seated bleeding in muscles and even works for the well known "blood nose".
Apply a few drops of wheatgrass extract inside the bleeding nostril with a cotton bud/Q-tip, then pinch the front area of the nose (where the bleeding normally comes from) with finger and thumb. Breathe through the mouth, not the nose. Bleeding usually stops in about ten minutes. If it persists, seek medical assistance.