Well at least you can still move it ,first remove the adjuster nut for the foot brake at the rear brake panel.. Then try the pedal again just to make sure it's not your rear cable dragging (but it's probably your pivot siezed)..If it's not the cable you have to remove the cotter pin & washer from the pivot , you should already have the brake adjuster nut off .. I take the right foot peg off & the fender brace ,depending on how siezed it is you may need heat (but if yours is still moving you should be ok) ..Now unhook the rear cable from the frame mount ,and with gloves on work the brake peddle up and down while prying off a little with a big screwdriver or pry bar.. It will come off just keep going up and down while prying .. Once it's off clean the peddle & pivot up with sandpaper and put anti-sieze on it .. (grease will do if you don't have anti-sieze )..
There is a seal on the end of the peddle hole they and there to hold out water & dirt but don't work very well..