put a pin in

verb4

1. •
   To postpone; to stop focusing or working on (something) until it can be finished at a later time.
2. •
   To discredit or ridicule; to deflate someone or something that is pompous or overly esteemed.

   • On the other hand, the lecture which puts a pin in professional egos and provokes opposition, may well turn out to carry the seed to future professional growth. — 1973
3. •
   To make something certain; to nail down.
4. •
   To mark well; bear in mind.

   • I am no upholder of party cries at electioneering times, but nevertheless I would advise all our readers to put a pin in that lot. — 1885