My advice after years of dealing with a stiff back the day after playing and more recently (last year) getting rid of it. I've had several acute issues throughout the years and you need that to subside and then get into a maintenance program to avoid future flare ups. Once a back is compromised, from a structural issue (disc/nerve issue) not necessarily a muscle pull, it will always be susceptible to future issues (although I'd say a grade 3 muscle tear is similar in terms of need to be careful in the future).
Hard to prescribe a specific regimen but I'll talk in generalities. Above all, don't freak out things will get better with time, you just have to come to know your body better now to head things off at the pass in the future. Welcome to aging. Ibuprofen is good for all of these along with these rehab techniques. Look at YouTube for stretches once you isolate the muscles that are related to injury.
Here are the different types of situations I've run into:
Full on acute throw your back out
Usually spasms come with it, structural in nature causing referred pain or numbness (4-10 weeks with rehab) or muscle pull (2-3 weeks with good rehab)
Light to moderate spasm after playing (low/mid grade muscle pull (ice for first 2 days, alternate heat/ice after that, wait until you can twist or stretch without spasm, start progressive stretching/massage to loosen/align muscle fibers, then some strengthening/light playing w/compression wrap) or it could be a
beginning structural issue where your stop as soon as you feel the first spasms, body is trying to warn you of future issue coming on - you might be able to head off at the pass by stretching and deep tissue massage, and some icing/ibuprofen immediately
Achy back after playing (later that night or next day) - usually stretching, if have money deep tissue on hams, butt and psoas, heat could help but ice feels better initially, ibuprofen could help depending on severity, daily maintenance foam rolling/soft ball rolling on glutes as an alternative to deep tissue massage if you can't afford it ; drink a lot more water before playing and do some dynamic stretching/warm-up before playing
Locked up back after playing, can touch shoes - similar to a full on acute back issue but it's not. Usually has happened after I went drinking and played the next day and sweat a lot, so essentially in cases of extreme dehydration, the muscles stop relaxing and lock up. It could be they're really protecting something which takes you back to #1, but a few times, I've found hydrating, a massage and then gentle stretching later that night will get you solid in 2-3 days. Consider this a false alarm the reminds you you're not 18 anymore
Hope that helps. I wouldn't freak out about nasty MRI's either, unless it directly matches a difficult nerve impingement issue. Then there are other options like cortizone shots and more severe alternatives