I've never seen the Nikielski's in my family spell it with a Y, but you never know. I do have records back to 1872 in Porgozela Poland/Prussia. There too, it was an I ending.
I don't have a tree on ancestry. I'll try to put one on this year. I do have the other side of family on there, and I don't have a paid acct, so I don't think you need one for a tree.
How do I see your tree.
My Nikielski's were Jan and Andrew and their sister Mary Suchar, immigrated in 1880s to Chicago IL.