Anger is a normal and natural emotion, and there is nothing wrong with having feelings - you are human, after all. You have the power to decide how to deal with this emotion you are experiencing.
All you really need to do right now is take a few moments just to relax, for you, to help you feel relaxed and calm. It feels good to relax. After this short relaxation session is over, you can proceed with your day, and react in a way that you choose.... relaxing for a moment now will help you to react calmly, rather than acting out of emotion.
It's okay to be angry. Just allow yourself to feel however it is you are feeling right now, noticing this feeling, but not reacting just yet. All you're doing is observing. Emotions are neither right nor wrong... they just are.