Japanese with Manga

Contracting 〜る＋な to

Grammar: Colloquial and Casual Speech

In rough casual speech, a verb ending in 〜る followed by prohibitive な may contract to 〜んな: 触(さわ)るな → 触(さわ)んな.

Examples

Don't worry with すんな

Learn the meaning and usage of the grammar 〜んな in Japanese, with examples from manga.
俺物語!! » Volume 6 » Page 56

Takeo takes his pregnant mother to the hospital, as she’s getting close to delivery. Once there, she gives Takeo and his friend Suna a list of things to take care of during her stay.

母(かあ)さん:
「大丈夫(だいじょうぶ)から心配(しんぱい)すんな」
“I'll be fine, so don't worry.”