The striker upset Napoli management after refusing to return to Naples last week as he received treatment to a hip injury at home in Belgium.
It was reported that Lukaku's decision had put his future with the Azzurri in jeopardy.
But taking to Instagram on Sunday night, Lukaku explained his side of the story: "This season has been very difficult for me, between the injury and the personal loss. I know there's been a lot of noise about my situation in recent days, and it's important to clarify the whole situation.
"The truth is that in recent weeks I haven't felt well physically; I had some tests while I was in Belgium, and it turned out that there was inflammation and fluid on my hip flexor muscle, near the scar tissue, as this is the second problem I've had since I returned in early November.
"I chose to rehab in Belgium so I can be of assistance when I'm called upon. I think most of you saw the interview I gave in Verona. I could never turn my back on Napoli, ever.
"There's nothing I'd love to do more than play and win with my team, but right now I need to make sure I'm 100% fit, because I haven't been recently, and that's had a mental impact.
"It's been a busy year, but in the end I'll make it and help Napoli and the national team achieve their goals when I'm called upon. That's all I want."