Matur nuung sewu. Aku inggin belajari Boso Jowo.
"Nuwun sewu. Aku pingin sinau Basa Jawa."
1. Not "nuung", it's "nuwun".
2. If you want to say thank you, you use "matur suwun" (literally meaning "(I) say/express gratitude"), but if you want to say excuse me, you use "nuwun sewu" (literally meaning "excuse me for a thousand time").
3. "Ingin" (not "inggin") is Indonesian word, not Javanese. So is "belajar" (not "belajari").
Thanks for learning Javanese! Good luck!