Wht should i do just a plaster?

its hard to say without actually seeing the cut, but it sound like you have done the right thing by washing it and putting savlon on it and letting the air get at it after it had stopped bleeding, it sounds like it was just a bad cut and doesn't require any medical attention - dont worry about the throbbing as that is normal with a bad cut, if you are worried about it then why not make an appointment to see your doctor, you dont need your dads permission to visit your doc, its a pity you dont feel you can tell your dad and ask his advice, just continue to let the air get at it and it will scab over in a day or two and it should start to heal in a couple of weeks, hope this helps sweetheart