Well, you need to stop the bleeding and then seek emergency services.
You should apply a damp towel or something similar to the wound and apply pressure. If it has been bleeding for 15 minutes then you will have most likely slightly cut an artery or hit a blood vessel. Just try to relax and don't panic about the amount of blood. I would advise you go to hospital or general practice as soon as possible. Don't drive yourself, get a neighbor or relative to do it for you. The last thing you want is to crash or lose concentration on the road. If you are finding it too hard to slow the bleeding then call an ambulance.
If you are waiting for a relative, neighbor or friend to arrive. I would advise you frequently flush your wound with cold water. NO Soap or other mild detergents. Apply pressure and wait.
If the bleeding stops then keep a very close eye on it and apply an antiseptic. I would advise even if you don't want to, is to go the doctor as you could get tetanus or a nasty infection that could cause serious problems.
If you have any issues then please state on your question.
Happy to help.
I am a doctor.