Could it be a pair of 8's or 9's and he's repping a 9/10? I don't see any SC's in his range, he's a straight up Nit.

Call?

PokerStars - $0.02 NL - Holdem - 8 players
Hand converted by PokerTracker 4

MP: 150 BB (VPIP: 10.00, PFR: 10.00, 3Bet Preflop: 3.13, Hands: 81)
MP+1: 50 BB (VPIP: 12.60, PFR: 7.09, 3Bet Preflop: 0.00, Hands: 127)
CO: 250 BB (VPIP: 5.91, PFR: 0.79, 3Bet Preflop: 0.00, Hands: 256)
BTN: 108 BB (VPIP: 18.53, PFR: 10.78, 3Bet Preflop: 4.00, Hands: 233)
SB: 46 BB (VPIP: 39.13, PFR: 8.70, 3Bet Preflop: 0.00, Hands: 24)
BB: 253.5 BB (VPIP: 13.04, PFR: 8.70, 3Bet Preflop: 0.00, Hands: 23)
Hero (UTG): 246 BB
UTG+1: 219 BB (VPIP: 15.31, PFR: 4.08, 3Bet Preflop: 2.63, Hands: 100)

SB posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has A A

Hero raises to 4 BB, fold, fold, fold, CO calls 4 BB, fold, fold, fold

Flop: (9.5 BB, 2 players) 5 T 2
Hero bets 6 BB, CO calls 6 BB

Turn: (21.5 BB, 2 players) 6
Hero bets 16 BB, CO calls 16 BB

River: (53.5 BB, 2 players) 7
Hero checks, CO bets 24.5 BB,

Getting 3+ to 1 I call. He's got overpairs in his range, plus sets obviously. I doubt his range includes things like suited connectors. Not much else to go on. Nits don't usually bluff.

Vimes

I probably just be river myself and fold when raised.