Remember that you can also get other benefits
If your boss cannot offer you a raise, consider other alternatives. For example, you can negotiate more vacation time or a flexible work schedule. Most employees would prefer new or additional benefits to a pay increase. So, consider what may be important to you.
If you want to ask for additional benefits, be sure to do your research beforehand to find out what is typically offered in your industry. This will help you make a more informed case for why you deserve those benefits!