Puncheon became the butt of fans' chants in the second half after he was forced to go for a pitstop.
Pochettino said: "That's the second time that's happened to me as a manager.
"Jason was feeling a bit 'unstable' and had to go to the loo.
"It was a nervy day. Whenever there's a new manager, the players want to impress and those nerves can get the better of you."