What's your sharing policy?
Only child?
What's your space like? Is there any where he CAN put special items, or things he isn't done with yet?
I have a dck in care who was booted from a center. She's amazing for me. Same issue (aside from others)
What I do- NO forced sharing. He can keep it as long as she wants, and we say "When you're done, can X have a turn?" and help facilitate that when the child puts the toy down. we sing- "YOU CAN TAKE A TURN, AND THEN I'LL GET IT BACK!"
They each have their own bins, they can place toys in there they want to save for later.
How verbal is he? we make name lists for turn taking of popular items.