Should I ask my boss for a raise?

It is always best not to keep things to yourself because they will often escape when you least expect and want it. By keeping it in you will build resentment against your coworker and against your boss. Therefore, without mentioning your coworker, you should speak to your boss and remind him of your dedication and your achievements and then request the raise. By bringing up your coworker to your boss you are in essence questioning his judgment. Speak to him in a calm and convincing manner and I hope you succeed in convincing him.