Can a Sony lens go on A Nikon body?

I'm looking to get a fish eye Lens or a Wide converter and the cheapest are Sony, But would Sony's lenses go on my Nikon D3100?

It might, once. You could put it on by force but it would permentently damage the lenses and body. Lenses companies make their lenses so they will not gone on competitors bodies. There are few exceptions but not in your case don't do it.

No. Nikon lenses are better anyway. Look into Sigma and Tamron lenses if your on a budget.