Just took off for a little flight and got a red bad battery cell warning. Do i need a new battery or can it be saved? Not sure what to do?

Don't panic just yet.  Just fly with your spare battery (uhhh, you DO have a spare battery, right?)  You can get some detailed info about the batteries (as well as a lot of other stuff) by uploading the Flight Record to HealthyDrones.com.  Instructions are on the website and its free.  

Try cycling the battery by running it down to 6-8%. I keep my Phantom or Inspire running on the ground (I bring the motors up here and there) until it shuts itself off. Let the battery sit for a few hours at room temp. then charge it, let it cool, and try again. You can see the cell data in the GO App. You may have to do this more than once. After a couple of tries and no success. New battery time. I also number my batteries and use them in succession.