The Brazil international has appeared fleetingly since moving to San Siro from Santos last August and was granted just a sixth substitute outing in Serie A with the deadlock still intact at Stadio Renato Dall'Ara.
But the Rio 2016 gold medallist found the breakthrough from close range in the 81st minute before removing his shirt and tearing towards the travelling support for joyous celebrations.
"I am very happy for this moment, for the first goal – even more so because it gave this important victory to us," he said. "I waited for this moment, I worked hard, because I knew that in one moment I would score. This moment will never leave my head.
"Since my arrival here I have worked hard, with great seriousness and professionalism.I know how much I can help Inter.
"I came to make history and never let my head drop. Let it be the beginning of a new history."