My back is in almost excruciating pain . What should I do? Is this a pinched nerve?

Diagnosis: Y-spine, FND, DCD, SPD, GAD, depression, IBS, visceral hyperalgesia. I don't drink, smoke, or use any recreational drugs.

Because this is the internet, I do not wish to share my real age but I am female (my pfp is of a livestreamer but my sex is female), never had back problems before except after vacuuming. I've been able to climb hills, pick up the baby in the family, squat, etc. I do have a very weak core and am going back to PT.

I put together a puzzle of my family and I was sliding it onto a board so there would be room for the 2,000 piece puzzle I'm starting. I stood up and all of a sudden I felt this sharp pain in my lower spine/back It hurt to walk, it hurt to bend, I'm sitting right now and it's only hurting a little bit but bending down hurts, squatting hurts, walking hurts, etc. and that pain is nearly excruciating. I rubbed my hand down my spine and looked in the mirror and didn't feel or see anything unusual. Does anyone have any kind of idea what this is and how I fix it? My job requires me to walk and I'm going to have to be able to walk by evening.

Thanks!!