Sit up, lean forward and put your chin on your chest.
Grab the fleshy part of your nose and pinch the fleshy part against your face between your thumb and forefinger (like a clothespin). Squeeze tightly for 15 minutes and this should stop most bleeds. Do not blow your nose after this maneuver or you will blow the clot off and it will bleed again. If the bleeding doesn't stop see an md.