If you’re proficient in daggers and crossbows, could you utilize something like a crossbow bolt AS a dagger?

in this vein:
If yourre proficient in daggers and crossbows, could you utilize something like a crossbow bolt AS a dagger (1d4 piercing) in melee?

Its technically a part of a weapon youre proficient in, used like one youre also proficient in…

— BC Jesse (@Ghost_Hack) September 9, 2018

Want to use a crossbow bolt as a dagger? Check out the rules on improvised weapons in the "Player's Handbook" (p. 147) for how to use weapons in unusual ways. #DnD https://t.co/XJ1jnVoVQK

— Jeremy Crawford (@JeremyECrawford) October 3, 2018