PokerStars No-Limit Hold'em, $2 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG+1 ($336.20)
MP1 ($292.05)
Hero ($200)
MP3 ($309.80)
CO ($260.80)
Button ($125.15)
SB ($181.50)
BB ($229)
UTG ($85.70)

Preflop: Hero is MP2 with J, J.
3 folds, Hero raises to $8, 1 fold, CO calls $8, 3 folds.

Flop: ($19) 5, 3, 2 (2 players)
Hero bets $14, CO raises to $31, Hero ???

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Villian is unknown.

What's your move after the raise?