Repotting seedlings from peat moss

[mostafanbl]

I have a sprout in a plastic cup with 75% peat moss 25% sand. I have found out that peat moss is highly acidic and would be harmful
How should I act? Should I repot in regular soil? And at which stage/seedling size would a transplat be neither late nor unsafe?

 

[InTheShed]

How's it doing? Does it look stressed? If not then let it grow some roots before you move it.