We don't know. Maybe she is maybe she isn't. Regardless Twitter is not an official record of anything and additionally they are selective with regard to what inaccuracies they censor.
That said, apparently swollen testes are reported in the VAERS as a reaction to the vaccine. Not a great amount but also non-zero.
Nikki Minaj didn't tweet about a "bad reaction" but a completely fabricated third or fourth hand story about someone's balls swelling up.
She was also not banned. Twitter literally said they were taking no action against her.
Nikki then tried to rile up her fans by crying "I'm getting cancelled" despite the fact that she was clearly not.