Time is short- you need to get injected ASAP.

I had both of my heels injected 5-6 years ago. That was the only thing that cured my plantar fasciitis and I've had no relapses.

It should burn and sting like a sonofabitch at first- that means they injected the right spot. Then stay off it til the last minute.

Good luck. Could be worse- Morton's neuroma which can cause you sever sharp pain even when laying down and is exacerbated by tight shoes.