A gaping hole in the heart
Each passing day, Tony feels his head ache worsen, now migraines he can understand but what he couldn't figure out was why his heart was hurting, not in a physical way. More like somebody poked a hole in there and left it wide open for the wound to fester. Except, this hole was now starting to seem to be shaped like a human ever since he picked that photo up.
He's had Friday scan the photo and bring out copies to assess it himself. Each time he picked up the photo, he could hear a boys' voice calling out to him, "Mr. Stark". Sometimes, he would hear the boy call him in anguish, sometimes with joy, sometimes like he was saying goodbye. The last one stuck with him, no matter what he did he couldn't get that voice out of his head, though it didn't sound like it was coming from around him and he didn't exhibit any more symptoms, he scratched schizophrenia off the list of things that could potentially be wrong with him.
This voice came from some place distant, like a dream he was reliving. Every time he fell asleep he would hear that voice, not taunting him but comforting him, telling him it's not his fault, telling him to enjoy his life.
One day, he finally managed to croak a few words out when he dreamed of the boy again with the kids' back turned to him.
But what's not my fault? I am enjoying my life. Who are you?
The boy in his dream turned back to him ever so slightly, "I'm nobody", with a smile and faded into dust, quite literally.
That night he woke up alone in his bed, "PETER!". It was finally coming back to him.
Spider-Man
Queens
The civil war
Thanos
The blip
The kid
Time travel
Thanos
The kid
Spider-Man
Dr. Strange
His kid
HE FORGOT HIS KID!