I'd consider stuck flaps to be a fairly major thing, I'd be more worried about the potential cause being some sort of control restriction somewhere in the linkage e.g. a spanner or something lodged somewhere that could migrate elsewhere and cause further grief to the primary controls, so I'd probably RTB. If found before takeoff I'd definately not bother flying and get it checked pronto.
Continuing flight with the flaps stuck extended seems pointless to me - so much extra drag, fuel burn and time, plus the above concerns. But each to his own judgment I suppose.