I hate the folk on AB who answer a genuine question with a question of their own because that makes it look as if the question has been answered when it actually hasn't!
Anyway, here goes: Do you have the make / model of the tap assembly? The manufacturer's website may well give you a clue as to how to replace the O rings. Are you sure that there isn't a grub screw? The one on my mixer tap spout is hidden round the back and is a pig to get at unless you have yery short screwdriver.
I'm sure that the answer isn't to exert force. If you can locate the grub screw all that will be required is a little waggling to remove the spout.