のにな

if only; I wish

→ の
phrase Uncommon #11,088
if only; I wish A sentence-ending expression of regret, disappointment, or an unrealized wish. It is often used when the speaker feels that something could have happened or wishes it would happen. The な may be extended to なあ for emphasis.
JA: もっと早く言ってくれればよかったのにな。
EN: I wish you had told me sooner.

いつもそうしてくれたのにな

You always used to do that for me.

— 罪人たち (2025)

私にお金があったら買えたのにな

If I had had the money, I could have bought it.

もう少しで満点とれたのにな

I was so close to getting a perfect score.