I don't think you have to worry, wherever he got it from it's healed by now. The scar will get smaller in time and he is not hurting from it.

Our Fister got scratched on his ear a few years ago by another cat, he still has a scar - see some pics of him on other threads, it's quite visible, but it's no problem at all! The evening it happened, he was definately shaken. :ekk:

I take it, you've looked at both ears? It's not the little double opening on the lower part of his ear you're referring to? All cats have that - and it probably has name.