Sandino was a communist rebel leader during the US occupation of Nicaragua in the 1920s to 1933. During the Sandinist regime and civil war in the 1980s he was very much honoured (mostly by left-wing supporters) hence he appeared on Nicaragua's coins.
After the war, when a more moderate government took over, coins with peace doves succeeded the old coins. On top of that the Nicaraguan currency had become so worthless that the old coins were not used anymore anyway.
More about Sandino himself:
https://en.wikipedia.org/wiki/Augusto_C%C3%A9sar_Sandino