Why on earth would you wanna pitch something to Nick after all the shady shit they've pulled, especially in the last five years? The executives are sitting on a mountain of original "shorts" that will never be developed into full series because SpongeBob and reboots are apparently the only things that bring in the money now.
And while Nickelodeon was a TV cartoon titan back in the '90s and 2000s, they still treated many of their shows like garbage. There's a greentext chronicling all their fuckups that I've seen floating around on /co/, and some of those bullet points may surprise you.
Seriously. You're better off aiming for Disney TVA, Cartoon Network Studios, DreamWorks TV, or Netflix Animation. Nickelodeon ain't shit.