Had it many times. I've done a lot of damage to my feet... I'm something of an expert in caring for my own tootsies now. Here's what I found useful in permanently squashing it.
I suggest avoiding further cortisone if possible. I've torn ligaments in my feet five times, and I'm pretty sure that weakness may be the result of numerous cortisone injections I'd received over the years. It can weaken/soften tendons & insertion points over time.
If your house/office/etc. has tile, concrete or other hard flooring, wear supportive shoes at all times
. Personally, I rarely wore shoes in the house, so it was a strange & foreign concept for a while, but... I got used to it. Athletes' foot can also become a problem from constantly wearing a shoe. I've taken to owning 3-4 pairs of running shoes (I switched to ASICS gel after 20 years of Nikes, they're much better IMO). Rotate shoes daily. Hit them with unscented Lysol once every week or two to disinfect. Gold Bond powder helps (put it in your socks) too.
Ice baths. Not ice packs - ice baths
. Fill a basin with cold water... and get in there. I can't tolerate water much colder than 50-55 degrees (yes, I measured) so I use cold water and add ice until my foot goes numb. The first time you do it, it's gonna be pure torture. Hang in there for 20-25 minutes (no more, no less), twice daily. You'll hate it, but it was the best, quickest remedy I found.
Finally, get a Bosu trainer
(or other balance trainer) and use
it. I used to just stand on mine and try to remain stable while watching TV (it's much harder than you think if you have weaker feet). Haven't torn anything since I started using a Bosu.