When Matt meets with Poindexter, Poindexter says I need to be outside, then Matt says I dont trust you and proceeds to smash Poindexters face into the table - which is what lead to Poindexters tooth coming loose so he could then use it as a bullet. Matt knows he's Bullseye and can use anything as a weapon
Yeah I'm interested as to what we were supposed to understand there.
Matt walks up to Poindexter, smashes his face into the table three times but in a very controlled way, not obviously in a fit of rage, and Poindexter
immediately seems to see this as Matt attempting to help him, presumably by sending him to the infirmary. Going to the infirmary potentially buys him time in which it'll much harder to murder him (because people would have to revise any plans that relied on him being in gen pop etc.), and also potentially would afford him more of an opportunity to escape.
It's unclear if:
A) Matt smashed him
just out of being angry with him. Problem is this doesn't seem very in-character, because he's not hugely worked-up and also didn't seem at all like uncontrolled rage, and Matt isn't a bully or a sadist, so it seems unlikely he'd derive much pleasure/satisfaction from a precise attack he then immediately lied about. Like if Matt was "flipping his [crap]", like getting increasingly unhinged, I'd definitely see just this, but that wasn't how the scene was played
B) Matt smashed him to send him to the infirmary and thus prevent him being murdered for a short time (probably more because he thinks Poindexter has info than anything else). That Poindexter immediately reads this as being helped supports this.
C) Matt smashed him to send him to the infirmary in order to let him escape. As
@Morrus says, this seems far-fetched.
To me it seems like B or a combination of A & B (i.e. I can buy some time and smash this awful guy's face in, win/win!) is the most likely, but because this show has essentially be massively retooled, it's also possible some of this is just from when the previous, less-competent showrunner was in charge, and thus produced accidental mixed messages or unneeded ambiguities.
(As an aside, minor point but I don't really believe Poindexter would have gone for Fisk's heart with the sniper rifle, he'd have gone for the head - he nails people in the head with imprecise tools from a distance constantly - but I guess it had to be the heart because Fisk is so much bigger than Matt he wouldn't have been able to body-block it otherwise - also 7.62mm at that range would probably go straight through Matt and into Fisk anyway, but like, dramatic licence I guess.)