Can canker sores - not cold sores - be popped? Can they appear on lip?

Not on lips. A canker sore is painful sore or sores inside your mouth -- on the tongue, soft palate (the back portion of the roof of your mouth), or inside your cheeks and not on the lips. The cause of canker sores is unknown. If it is on your lips it may be a cold sore so i would not recommend popping it.
Scarring. No, do not pop. Canker sores form inside the mouth and should not be popped. Cold sores form on the lip and should not be popped. Talk to your Dentist about emollients you can put on the lesions to provide relief.