Side/Rib Pain from Deadlifts?

NLP week 6. (45 year old male, 276lbs 5'8").
Have not started alternating with power cleans yet.
Last two workouts I've felt pain at my sides along the ribcage (not at the bottom, but more centered). Though the bottom sides are also tender. Getting down onto the bench for bench presses was also painful in this area. After a nights sleep, pain much reduced, about 50% of what it was yesterday. Today, raking leaves hurt in that area.

I use a 3" belt for my last warmup set, and work set.

Last training session dead lifting, I definitely felt the muscles there working (or at least I felt them making themselves known). About an hour after the workout, just getting up from the couch was painful. I want to describe it like severe soreness.
I'm not savvy with anatomy, my googling didn't give me a clearer answer. Is it possible these muscles are sore from deadlifting?

It's been now almost two weeks since the initial onset of pain. Pain was originally more centered on ribs, felt on both sides, and more dull. Hurt more on left side than right.

Now, notably, the sharp pain is now completely limited to my right side lower rib cage area towards the front. Sharp pain when getting into a laying position, rolling over in bed, or getting out of the comfy chair.

I de-loaded (after online consult with an SSC) everything. Pressed one work set of 5 yesterday (no pain in warmups), but started to edge in on the work set on both sides. (Press at 107.5lbs). Stopped after one set.
Deadlift: I'm still feeling the tension in the area with the pain mounting as I progress through warmups, so I went very light yesterday on work set (140lbs) to see if I'd have the massive onset of pain afterwards like at original symptom onset.
On Friday's workout I'll split the difference between this and the recommended de-load rate (230lbs) the coach specified and see what that does.

Squat has been unaffected by this injury, FWIW.

Anyone have a feeling for what is actually injured here? If it was muscle, shouldn't it have cleared up within 11 days? I am 11 days out from the workout where things went "ouch".

Based on movement descriptions, it sounds like a muscle strain and this can last a few weeks. Its important to continue to train but keep pain levels low. Regarding the DL, you can try a rack pull. It will be an easier position to get into while this heals up.

For anyone interested. It ended up being about 4 weeks, but things seem to have healed up. I deloaded deadlifts down to 135lbs and worked my way back up to 295 (which was PR/injury) over about four weeks. Up to 320 now.