He is showing you his scars over his body.

Izuku promised he'll come to your dorm, he did as he said.

"Darling, I think I can show you all my scars!" Izuku said with a smile. Then he unbuttoned his t-shirt... showing you his abs.. but scars too.

"Do you think.. they're ugly?" Izuku asked, hoping you'd say' 'no'.