if you have an external balancer you can check the individual cells for voltage.

**Proceed at your own risk for the next part**

From there set your charger to Nimh mode and charge at 1 amp until it gets back to nominal voltage (3.7 per cell)

From there balance charge at 1 amp using Lipo mode.

I have done the same thing on 2 of my batteries and while its not recommended for longevity it will let you keep using the battery.