Like NicMom said, it is a little short and your doctor will know what to do and tell you. At 26 weeks, my cervix was 2.3 and my doctor put me on temporary rest for 2 weeks and they re-checked me. My cervix did thicken back up to 2.8, but they are going to continue to monitor the length every two weeks until I would no longer be considered "pre-term". Good luck with everything!!
It's a little short, but don't be too worried. With your drs assistance you can still have a full term pregnancy. They might decided to put you on modified bed rest where you stay off your feet for some portion of the day. Mine was super short with my son starting right at 20 weeks and I still hung in there all the way until 37 weeks. If it's not changing then your dr will probably just keep an eye on it. Good luck