Try applying super glue to fix your broken glasses arm. Or you can use sticky tape to fix the two parts together. But it may look strange. If you can't fix your broken glasses arm, you can take them back to the place where you bought them and ask the staff there to help you fix your broken glasses arm. They may have the ability to fix any broken eyeglasses arm. If they can't, you should buy a new pair of eyeglasses which won't cost you too much.
Some glasses factory has a number of professional technicians, they have many years of experience in the production of glasses, they can engage in a variety of glasses repair and welding work. For a broken glasses arm there may have several specific situations, the easiest way is to go to the glass store, these professions can help you out. If still under warranty, it can be returned to the factory to change.
It may depend on the material of your glasses. You can firstly try to use your super glue to stick it. Once I met the same situation with yours, I tried to use super glue but failed. If this way can not work, you can bring them to the store where you bought them. There are professional staffs in most of glasses store. Perhaps they can help you to fix them. But even if they are fixed, there must be scars left. It is better for you to change another new one.