i recently bought a carbon steel frying pan, and seasoned it as the instruction says. but i noticed that the inner bottom of the pan turned dark after i had it seasoned, especially after my first use. the inner bottom looks like it's burned and it looks like a rust or something . i tried to remove it using scouring pad and sponge but it just won't go away. it also has a bad smell even after washing it.

should i still continue using it? is it hazardous to health? how safe are carbon steel frying pans for health? how could i remove the discoloration?