early in tournament. no ICM implications
Hand History driven straight to this forum with DriveHUD 2 Poker Tracking Software

NL Holdem $4+$0.40 (800.00BB)
BB ($18400) [VPIP: 0% | PFR: 0% | AGG: 0% | Hands: 5]
UTG ($55985) [VPIP: 22.6% | PFR: 12.9% | AGG: 44.4% | Hands: 31]
EP ($23300) [VPIP: 27.3% | PFR: 9.1% | AGG: 20% | Hands: 11]
MP ($81798) [VPIP: 22.7% | PFR: 13.6% | AGG: 12% | Flop Agg: 0% | Turn Agg: 0% | River Agg: 60% | 3Bet: 0% | 4Bet: 0% | Hands: 44]
HJ ($22546) [VPIP: 36.1% | PFR: 27.8% | AGG: 19% | Flop Agg: 30% | Turn Agg: 16.7% | River Agg: 0% | 3Bet: 8.3% | 4Bet: 0% | Cold Call: 23.1% | Hands: 36]
HERO ($40389) [VPIP: 27.4% | PFR: 19.2% | AGG: 20.2% | Flop Agg: 31.7% | Turn Agg: 22.3% | River Agg: 23.3% | 3Bet: 7.4% | Fold to 3Bet: 57.7% | 4Bet: 10% | Hands: 1079]
BTN ($86804) [VPIP: 26.5% | PFR: 17.6% | AGG: 48.5% | Hands: 69]
SB ($24138) [VPIP: 12.5% | PFR: 6.3% | AGG: 30% | Hands: 48]

Dealt to Hero: A J

UTG Folds, EP Folds, MP Raises To $1700, HJ Calls $1600, HERO Raises To $5371, BTN Folds, SB Folds, BB Folds, MP Calls $3671, HJ Calls $3671

Hero SPR on Flop: [0.96 effective]
Flop ($17813): 2 8 7
MP Checks, HJ Checks, HERO Checks

Turn ($17813): 2 8 7 4
MP Checks, HJ Checks, HERO Checks

River ($17813): 2 8 7 4 A
MP Checks, HJ Checks, HERO Bets $7120 (Rem. Stack: $27898), MP Raises To $41573 (Rem. Stack: $34854), HJ Folds, HERO Folds
am I a nit?
I feel like he's just representing only an ace that made 2 pair on the river

Yeah, I suspect you're right. You might even just check back this river since there aren't going to be many worse aces here in a 3-bet pot. (By which I mean, this deep AQ is often just calling pre.)

Your 3-bet should be larger this deep, especially over two people. You should kick it up to 7200 or so.

I don't mind the way you played this. Just wait for a better spot vs an opponent who clearly doesn't understand what they are doing. I don't like checking back this river especially in position.