Nigerians particularly those from the Ibo tribe at least in my experience have this way of saying nonsense as a phrase at the end of sentence or a sentence by itself as a means of showing their disdain or displeasure for something.
For example, he has a good job but he got caught stealing a t-shirt. Nonsense.
Or, she went to the airport without her passport expecting that they would let her fly. Nonsense.
Or in an discussion after the person you disagree with finishes speaking or presenting their argument. You reply: Nonsense… and then you proceed with your argument.
And even if the person is speaking in Ibo, the word nonsense is always said in English.