If you have white discharge per vaginum that needs to be treated.The cervical length is okay so complete bed rest is not warranted. But better restrict your work and do only light sedentary work and avoid intercourse.

Cervical canal diameter can not be 24 mm. 24 mm is almost ONE INCH . Which uterus can hold a pregnancy when its Cervical CANAL diameter is one inch ? So it is the diameter of the Cervical tissue (including thickness of the muscle mass of cervix) . And that is normal. To me it looks like  typographical error. For further information please consult with me on Practo.

It's the diameter of internal os that's important U hvnt mentioned that If more than 8 mm it's an incompetent os U need strict bed rest n a stitch called encircalage after 12 weeks