From the title of a YouTube video:
From the song じょんから女節:
I suspect the second usage might be a contraction of に and the 関西弁 copula や, but I'm not sure. Did the first one come from んにゃ <= んや <= んである?
There are a few places where にゃ is used in place of certain constructions, but is it possible that these are just someone trying to be cute?
The first one is a contraction of the phrase だるまさんがころんだ, which is a children's game similar to 'red light, green light.' Seems possible that using にゃ is just trying to be childish/cute/catlike in its pronunciation.
The second one is a contraction of には, which also might not be directly related to dialects and simply a contraction based on speech. So while this isn't really cute per se, it certainly could be, but otherwise it just strikes me as a normal contraction.