When you are in trouble, the most important thing is that you can save yourself. It doesn`t matter how you do it. If the mugger is a man the best thing to use is the groin kick. It may sound so old and dirty but believe me it works. The self defense doesn`t have to be difficult. Sometimes the most easiest stuff works best. Of course the mugger isn`t stupid you have to pick the right moment to do that. The right timing is the most important part of it. You have to get his attention to something else and then attack him fast and strongly. The groin is very gentle area for guys and when the attack is strong, believe me you will be safe.
You don´t need to kick him more if he is down. Now is the time to run and find some safe place.
But don´t forget that the groin kick is very serious attack. Don`t ever use it when you are not in serious danger. If some random guy bothers you in the club there are some other tactics what you can use. You could get in serious trouble with the law when you hurt someone without any good reason. Injuries may be permanent !!!