A word-for-word calque of 'inner peace'. It reads exactly that way.

What a Japanese person actually thinks
Reads like a UN pamphlet that got lost. 平和 belongs on a banner about disarmament, not on a ribcage. Mildly comic in the mismatch.

Meaning

Literally: inner + peace
Actually: Understandable, but 平和 is *political* peace — the opposite of war. Applying it to a person's interior is an English idiom translated with the wrong word.

Scores

Naturalness●●●●●

The grammar is fine, the word choice is wrong. Native speakers would say 心の安らぎ or 平常心, never this.

Coolness●●●●●

Long, hiragana-heavy, and it reads as translated. Nothing here is working.

Watch out

high平和 means peace-as-in-not-war. Using it for personal serenity is a genuine mistranslation, not just a stylistic miss.

Get this instead

安らぎ yasuragi
peace of mind; ease

The actual Japanese word for the feeling you mean. Soft and warm.
平常心 heijōshin
an unshaken, everyday mind

A composed mind under pressure. Common in martial arts and sport — reads as earned rather than aspirational.
泰然 taizen
composed; unperturbed

Two characters, dense, dignified. The tattoo-shaped version of the idea.

On skin

内なる平和

Orientation: either

N/A — change the words.