It all boils down to how sure you are that he is a scammer. If you are 100% sure that he's a scammer then there's no need of feeling guilty.
But if an Indonesian is speaking Nigerian that doesn't mean he's a scammer. People can speak different languages. I can speak 3 different languages as well.
Also, if you are using the money you received from that person for your own benefit then it's probably a bad thing.
You should consider one of the below options

1. Send the amount back to the person by researching more about him or ask him for his ID verification or video verification if he wants the money back
2. Donate the amount to charity