Try to persuade the dragon

You move inside the cave holding the egg, and calling the dragon. He arrives, with his eyes burning like a lava pit and his scales tainted with darkness and a purple energy.
But as you speak, something happens. The fire in his gaze dims when you show him the egg and tell him the story of the goblins. An ancient magic is around your body.

"You…" His voice rumbles like a distant thunder. "You have brought him back."
"You speak the truth, a traveler from another world risking everything and returning my son... I don't deserve that, I'm old and corrupted"

Slowly, you lower the egg into the nest full of smoldering embers. The moment it touches the warmth of its father’s magic, you notice a small fracture appears, then another.
A tiny claw pushes through, and with a final crack, the newborn dragon emerges, small, covered in ruby scales, and perfect.

The massive body of the giant dragon trembles. A single, tear falls from his eye. "I thought him lost forever."

But then his great head bows, his voice heavy with sorrow. "I cannot raise him. The curse that blackens my body would claim him too."

The dragon uses his sharp claw to remove a scale from his chest, you see his heart exposed, replaced by a magic stone that looks like a gem.
You understand then. This magic stone was never just a gem. It was his heart, hardened by grief, encased in stone to keep the corruption at bay and live a bit longer.

"Take it" He whispers. "Free me… and save him."

The dragon closes his eyes... You reach out, your fingers brushing the stone embedded in his chest.

When you take the stone the dragon's form begins to dissolve, not into black ash, but into red embers, rising like fireflies. The curse breaks...
And in his last moment, he is not a monster. You listen to a deep voice echoing in the air "Thank you, protect him"

The newborn dragon chirps, rubbing his warm head against your hand and saying: "Mommy... hungry"
What?? you have the stone in your hands, and you think about your options.

You can return to your world, and leave the little dragon alone.
You can return to your world, but bring the little dragon with you.
You can stay a few months and return to your world when the little dragon can take care of himself.