Should i tell the headmaster or not?

Today I was waiting outside of school with my mate eve. we was waiting for my other two friends lizzie and aimee. when they finally came lizzie looked and me and said common then started to walk really fast so i shouted to her "why do you always do this. This is why we always fall out because you leave me" as soon as i said that an 70 year old man and woman went by and gave me an evil glance and said something but i didnt quite hear them. So i kindly went up to them saying sorry but wat did say (not in a mean way) then they said you could wash your dirty little mouth out and i said why then they said that i swore and me and eve plus lizzie and aimee said i didnt say that then they started saying lots of things to me and for the record im 14 and never had a detension before and i really nice person. anyway bak to the story they started to say stuff to my friends then they slowly walked for about 3 seconds when my next door neighbour said something im not quite sure wat then all of a sudden the old man went up to him and grabbed his neck and said you shouldnt say that. he was been really threatning and dont forget we are only 14 then his wife said hes not worth it and we all said let go off him. so he did then he walked off and we got huddled into a big crowed walkin home. About 3 mins afterwords we catched up to them and i said excuse me but i dont think wat you did to that boy was right. then he said wat did he do and me and my four friends said you grabbed the boys neck and he said he didnt but about 20 people saw him do it. then he wife started sayin that she is glad her grandkids arnt like me and stuff like that then me and my mate eve said sorry but i really didnt swear you must of herd me wrong then the old man said do you want me to do the same to you as i did to that boy. then the lady said give me your name im reporting you to the non-emergency police and school because you swore even tho i didnt. then i said im not givin my name cause i dint do anything your the people in the wrong. then he just went right up close to me and said leave it and i said ok. then they walked off. wen i got home i was in tears ive never been treatend before. my mates said they will go with me to the head and tell him wat happend because at our school they take thiss very seriously. but im a bit to scared to cause what if the police get involved i dont want to get in truoble for something i didnt do. even tho i didnt do anything. i told my mum and she said i should tell him. What would you do please help!