My girlfriend is having intermittent moderate pain around the cervix two weeks after cervical erosion cauterisation. what may cause this?

That's not outside: of what would be expected with normal healing, although it's often difficult to interpret where pain in the vagina/cervix/uterus is actually coming from. Nothing should have been inserted into the vagina up to this point. I think it would be safe to just watch and wait another week or so; contact her doctor if she is concerned in the meantime, especially if discharge or bleeding. Best wishes:)