Wear glove if you are dealing with blood,and if you do not have access to glove then put cloth or something over the wound.
Next apply pressure to the wound for about 5-10 to stop the bleeding. If a blood clot (scab) forms then do not pick at it or the bleeding will continue.
After that you should elevate the injured area Then put a final bandage on and wrap it in place.
Or if it is not incredibly deep then wash it out with soap and water or hydrogenproxcide. Then put a bandage on it and leave it be.
Some things that may cause this to happen is falling and stepping on sharp objects these two are probably the most common.
It is incredibly easy to prevent you from falling or stepping on glass all you have to do is wear shoes and watch your step when you are walking .