Translation of "Ulcer" in Japanese

An ulcer forms in the stomach.

胃に潰瘍が出来る。

I have a ulcer in my mouth.

口内炎ができているのです。

When you start taking medicine it begins working on symptoms, like pain, right away, but that doesn't mean that the ulcer heals right away.

薬を飲み始めると、すぐに痛みなどの症状はとれてきますが、すぐに潰瘍がなおるわけではありません。