Hi everyone
First of all let me preface this by saying that I know I'm doing too much too soon.....

One of my friends talked me into doing a half century with her. The ride is this coming Sunday. I've been training for it for about 1 month now. And that is the extend of riding a bike I've done for about 15 years.
I have been a runner for several years so I'm physically fit/active, just not on a bike.

This last Sunday I did my final big ride of 40miles (the first 15 were a constant steady uphill with about 1700 feet of elevation gain).
I was spent by about mile 30, empty stomach, only protein and veggies night and day before the ride. But, I wanted to get my 40 miles in so I did a couple loops around my neighborhood. At about mile 37, I was coming to a stop and complete newbie mistake got my cleat stuck (again, should have stopped 10 miles ago!) and tipped over! Luckily I was going about 1 mph when it happened. No skin lost, but a nice bruise on one knee and tweaked the hamstring of the other leg.
Finished the ride and apart from the knee had no pain at all the rest of the day. Also on Monday, no pain aside from the knee.
Wake up Tuesday morning with excruciating back spasms! Not low back, more like right where the rib cage ends so I think its the bottom of the lat muscles. It's definitely on both sides of the spine more so than right over the spine.

I iced, took ibuprofen and pulled out the black foam roller. The ibuprofen seems to keep it to a dull roar but doesn't totally make the pain go away. The muscles do seem to loosen up if I'm walking around. But, as soon as the ibuprofen wears off the spasms start up again.
I woke up a few times last night, I think if I rolled over in bed the spasm would start. And I woke up barely being able to get out of bed again this morning.

Any opinions on if this is from cycling 2 days after the fact with no sign of pain earlier?