overpair faces flop aggression v. unknown (FTP 50NL)

[Montezuma21]

villain is complete unknown. what would you do?

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
5 players
Converter

Stack sizes:
hero: $49.35
CO: $30.95
Button: $82.90
SB: $21.50
BB: $41.90

Pre-flop: (5 players) hero is UTG with Q[img]/images/graemlins/heart.gif[/img] Q[img]/images/graemlins/club.gif[/img]
<font color="#cc0000">hero raises to $1.75</font>, CO calls, 3 folds.

Flop: J[img]/images/graemlins/diamond.gif[/img] 7[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/club.gif[/img] ($4.25, 2 players)
<font color="#cc0000">hero bets $4.25</font>, <font color="#cc0000">CO raises all-in $29.2</font>, hero?