I bit myself when I'm angry and that calms me down a lot and it leaves no much bruise. Why should I stop?

Because sooner or later it will get to the point where it becomes addictive and you start to bite harder (it is a form of self harm even if it doesn't leave a mark).

Personally, I don't think it is something you should do when you're angry just because it could eventually harm yourself if you bit down too hard or what have you. Maybe instead of stopping you could replace biting with something less harmful to you and your body if you can. Everyone has some coping ways when they have hit a certain emotion, I know when I'm mad or just really out of it, I notice I need to do something because my feet/heel will tap the floor a lot and very fast and then when I get time, I go running and that helps me, or I workout to kind of release that stress going on for me.

If it helps you calm down without inflicting much damage to yourself or others, maybe you shouldn't.

Biting yourself, is a form of self-harm. This means that hurting yourself on purpose is not healthy for you.

Because it is self harm, maybe not severe form of it but it is still self-harm and it is never a good sign.

that is not a healthy way to deal with your anger - there are many other things you can do to let your anger out

Because that is a form of self harm, it can lead to a mindset where you associate self inflicted pain as release and calm. This mindset can be very dangerous and lead to other methods of self harm, it is best to always find healthy ways to deal with frustrations long term rather than taking the sometimes easier quick solutions we see in the moment.

In my opinion, the action seems fine. But you are aware the behavior is not healthy, that's why you are doubting. And it's not something you would want to do in public. So it slowly has to stop. There are other method to calm yourself, meditation or yoga for starters.

Because you still to do it for the sake of hurting yourself. This won't solve your problems. Try to find something, that calms you down and makes you feel better instead of hurting yourself because it's not worth it and people care.

Self harm is a maladaptive behavior may escalate from seemingly harmless behaviors to potentially life threatening behaviors. Additionally, self harm is a result of not knowing how to cope with emotions and other underlying stress that likely needs addressing.