How can I control my anger? The only way I can let it out is by punching walls, my knuckle has swollen and very sore, how can I calm myself down?

Doc time. In controlled outbursts like that can lead to worse, more dangerous behavior. Please see a doctor asap.
Anger management. Everyone feels anger. How we express or act upon those feelings is something we learn, can modify and have some choice about. If your anger is causing injury to yourself or others, it's time to get counseling from someone skilled in anger management.