3/5: am I a nit for thinking about mucking this?

[kevdawg21]

3/5, live game. UTG is a solid TAG, MP is LAG.

Chips

UTG: $650
MP: $285
Hero: $500

Hero is CO with A [img]/images/graemlins/heart.gif[/img] Q [img]/images/graemlins/heart.gif[/img]

Preflop: UTG raises to $20, 2 folds, MP reraises to $50, 1 fold, Hero calls, 3 folds, UTG calls.

Flop ($155): A [img]/images/graemlins/diamond.gif[/img] K [img]/images/graemlins/diamond.gif[/img] 7 [img]/images/graemlins/club.gif[/img]

UTG checks, MP checks, Hero bets $75, UTG folds, MP raises all-in to $235, hero...?

Was calling PF bad? Should I have checked that flop? Is mucking here now profoundly sorry?