It is the most pain I have ever experienced and unfortunately even with treatment takes a long time.
My experience f NHS physio was that they'll just give you exercises to do at home, so don't wait for that, start now.
They did help me, but only once I realised you need to do them much more often than seems, reasonable throughout the day.
The regime that fixed me in the end was;
Ice. Lots of ice. Ever hour if you can, for as long as you can bear. Everytime you sit, have your foot on an ice pack.
Rolling pin. Roll your foot on a rolling pin before you first put a foot to the floor in the mornings, and then multiple times during the day.
Calf stretching. I found the one where you pull your toes up with a strap most effective. Again first thing, before first standing on it and throughout the day.
Also find a you tube video on scraping for Plantar Faciitis.
I paid for expensive custom made shoe inserts, but didn't find them helpful.