Dear Paul,
I'm sorry to hear that you have an arguement with your friend.Nobody is perfect,so don't be too sad.
It's not so bad because you have realized your fault.You should believe that your friend is tolerance because he is your friend.Try to write him a letter and express your apology as sincerely as possible.Give both of you some times to forget about this unhappy thing.During this time,you should think of yourself and maybe after some times,he will accept you again.Your friendship will never be end.
Hope you can get on well with your friend.
Yours sincerely,
Li Lei