“pain” in Japanese is 痛, read tsuu, ita (つう, いた). It is a Grade 6 Kyōiku kanji, taught in year 6 of Japanese elementary school, and appears in words such as 頭痛 (headache).
What does 痛 mean?
頭がとても痛い。
Same sound, different character — the classic trap. Compare them side by side: