The strange taste might be infection draining from your tooth/gum. Esp. if the dentist put cotton temporary filling in the nerve canals. If this is it, it should go away after a few days. You shouldn't be bothered by hot/cold if the nerve has been removed--there's nothing to be irritated anymore (at least in theory).
Just rinse your mouth out with some warm salt water occasionally and it'll help soothe any irritation.