Frankly, medical terminology isn't necessary and might even lead to increased confusion, especially after being translated. All medical terminology is not universal.
Just state your complaint in plain language as clearly as you can using layman's terms. I doubt that a Japanese doctor needs much more guidance from you than simply understanding your complaint. For example, you might say (in Japanese), "Doctor, I can't hear as well as I used to and I think it may be due to an injury to my ear canal some time ago. Can you please have a look?"
I would expect the doctor to examine both ear canals. If your theory is correct, the doctor won't need further explanation. She will see it with her own eyes and know what to do about it. She will probably also want to test your hearing in both ears. I would not be terribly surprised to find that the cause is something other than what you suspect.
Assuming that you don't speak fluent Japanese and he/she doesn't speak fluent English, you might consider bringing a translator along with you since the doctor will no doubt have questions and perhaps need to explain things to you. It's the sort of situation where language barriers can be troublesome and you don't want to risk misunderstandings.