English Translation
It was nothing but a joke.
“농담이,” can also be correct depending on the sentence structure. “농담이야” means “It’s a joke.” The difference lies in the emphasis and formality. “농담일 뿐이야” emphasizes that it is just or only a joke, adding a nuance of minimizing or dismissing any serious interpretation. On the other hand, “농담이야” is a more straightforward statement that it is a joke, without the additional nuance of dismissal. Both are correct but carry slightly different tones.