The is no option to directly delete your Nitro Type account. All you could do is to write an email to the Nitro Type team and ask them to delete your account.
You can find their updated email by following the below steps.
Log in to your Nitro Type account.
Click support from the drop down window.
Scroll to the bottom of the page.
Fill in the contact support form mentioning that you would like to delete your Nitro Type account.
Wait for their reply and in case you do not get a reply, send them a followup email.
You can also try tweeting by tagging Nitro Type Twitter account.
This will help you to get their attention to delete your account.