He actually does not think he can tell him. He can show him but he's afraid of startling him or forcing something Wei Ying doesn't want. He must say it.

He pulls back enough to see Wei Ying's face, expression pained as he tries to say what he has learned. "Can, can put mouth there," he chokes out, ears absolutely burning as he braces himself for Wei Ying's reaction. "Or can put myself there," he tries, gesturing downwards. "May be too much, tonight. Just, thought for future."