I have a fractured lower fibula and was in a cast then a boot then a splint. 2 weeks later I went to the ER and was told I have a non-union. Next step?

Non-union. Depends on the time of immobilization as to the determination of the non-union. Assuming you have been in the cast and boot for up to 12 weeks, this is possible. Next step is to see your doctor for re-evaluation and possible use of an electromagnetic bone growth stimulator. That is your next step. In the meantime back in the boot.