Being a bystander isn't also the right thing. Thought you may have to face consequences for a period of time, in the end, putting yourself into the victims shoes helps to better understand exactly what you should do.
Besides, if someone is doing this, and what they're saying is false, then I think that you should definitely "stick your nose into the situation and take a better look" . Speaking the truth is always right, though many fear the consequences.
Deal with the consequences later, focus on the present, and do what's right: TELL THE TRUTH.
The truth always has a way of getting out, and if you get caught in that, I think that's actually worse.
But then again, all of this is so much easier said then actually done.
Vaaheguru Jee Kaa Khalsaa Vaaheguru Jee Kee Fatehh!