I think i have anger issues, should I take up boxing or get professional help?

Im a calm collected guy of 17 whos plays sport (rugby and karate) and socialise lalala just generally normal school kid. I always bottle my feelings up and anger and grit my teeth etc and chill out afterwards, and have done so for years with my younger brother. Hes 15, but bigger than me and 10x more annoying and frustrating. today I punched him in the face, ive never hit him before, and i feel disgusted. my mum was so shocked and my dad hit the roof at how unacceptable it was. I cant even tell you why i did it he just pushed me over the edge. and im worried i actually ahve an issue here. I broke his nose and probarbly ruined our friendship and i dont know what the **** to do. do I go to boxing or something to vent my anger, or seek professional help? and if help, what sort of help should i seek?