Party Poker No-Limit Hold'em, $2 BB (10 handed) Party-Poker Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($278.39)
UTG+1 ($229.15)
UTG+2 ($37)
MP1 ($376.77)
MP2 ($50)
MP3 ($218.25)
CO ($237.80)
Button ($122.60)
Hero ($221)
BB ($34)

Preflop: Hero is SB with A, A.
UTG calls $2, 4 folds, MP3 calls $2, 2 folds, Hero raises to $11, 1 fold, UTG calls $10, MP3 folds.

Flop: ($28) 6, 3, T (2 players)
Hero bets $20, UTG raises to $50, Hero ????

Villain could be semi-bluffing with this board. However, he is running at something like 18/6/1 (over 80 hands only). He quickly calls my PFR. But he quickly raise FLOP.
If we call here the pot would be $128 and we would have $160 left.
What to do here?
If villain was a bit more aggressive I would be willing to stack off.