A:What’s wrong with? B:something/nothing/anyone,l’m fine

It looks like you’re quoting a dialogue. If you’re looking for a more natural way to present it, you might consider this format:

A: What’s wrong?
B: Nothing, I’m fine.

Or if you’re emphasizing that there might be something wrong:
A: What’s wrong?
B: Something, but I’m fine.

If you have a specific context or additional information you'd like to provide, I can help refine it further!