I beat up my best friend and injured him!?

we wer beaten up . So im 14 and hes 14 we both do bodeybuilding at same gym . i cant Explain we Like sameeeee . mass wait . muscle all . so Hes my best best friend from kg1 . we hang out alot. so i got a Girlfriend . and he dosent and hes jelous . so it was school day normal . until i saw him hiting on my girl friend and making here to break up with me and etc ... so i went to him and told him what u doing !!! my gf said nothing in Scared voice . so i looked at him in mad way . Fire in my eyes and punched him with all my might so he almost fell and punched me A really storng punch and we Traded blows until he fell and i Stomped him and he fell uncouncious and look on my gf and left while i was on my way i was bruised . and i was feeling so sad what ive done . hes my best friend should i beat him that way . ? what should i do APOLOGIZE ? or leave my gf . or leave my friend plz help me