Hello

I just arrive on the table and villain is unknown (2 hands only). I hesitate on the river

No-Limit Hold'em, $0.05 BB (5 handed) - Hold'em Manager Converter Tool from FlopTurnRiver.com
SB ($4.98)
BB ($5)
UTG ($9.05)
MP ($3.75)
Hero (Button) ($5)
Preflop: Hero is Button with K, A
2 folds, Hero bets $0.20, SB calls $0.18, 1 fold
Flop: ($0.45) Q, A, J (2 players)
SB checks, Hero bets $0.30, SB calls $0.30
Turn: ($1.05) 2 (2 players)
SB checks, Hero bets $0.70, SB calls $0.70
River: ($2.45) 7 (2 players)
SB bets $3.78 (All-In)
Total pot: $2.45

hero ?