PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

CO ($50.40)
Button ($49.55)
SB ($47.25)
Hero ($56.75)
UTG ($49.25)
MP ($62.75)

Preflop: Hero is BB with A, A.
1 fold, MP calls $0.50, 1 fold, Button calls $0.50, 1 fold, Hero raises to $3, MP calls $2.50, Button folds.

Flop: ($6.75) 5, 4, 3 (2 players)
Hero bets $5, MP raises to $10, Hero ???

---

Villian is a complete unknown.

What's your move here?