Your dentist may have given you some gauze to place onto the area where the tooth has been removed - if not, a clean cloth handkerchief will do just as well (but not a paper tissue).
Roll it into a small firm pad large enough to fit over the gap (probably around 1cm by 3cm).
Sit up and gently clear away any blood clots around the gap using the gauze or hanky.
Put a clean pad over the gap (from tongue side to cheek side) and bite down on it firmly for 20 to 25 minutes.
Take the pad off and check whether the bleeding has stopped. If not, apply a fresh pad and contact your dentist
Sometimes there may not be room in your mouth for your wisdom teeth and, as they start to come through, they push against the teeth already there or may start to come through at an angle. When this happens, you might feel some pain or discomfort, so the best thing to do is to visit your dentist.
The dentist will probably take an x-ray of your mouth to see how - or if - your wisdom teeth are coming through. From this, they will be able to make a judgement on whether or not to take them out, and how easy or difficult it might be. Extractions can also be done under sedation.