a la gran puchica
translates to something like "oh crap" (it doesn't quite translate well). you say it in sort of a "holy shit that was crazy" sort of thing. but its not really a swear.
The word puchica (with tilde in the u) is used as an expression of surprise, admiration, anger or fear by the jargon youth Honduras, Nicaragua, Guatemala and El Salvador and not has any significant meaning that is of an interjection and a euphemism.
Cuando Jose vio a su amigo por primera ves en diez años le dijo, “Púchica !! que gordo estas!!”