Were you lifting weights in your hand while doing squats ,n is the exact location of pain is lateral to the spine ,as u said it 3 inches above the ribcage I feel some amount of inflammation around the rib can be the reason.it would be better if u can visit a physio for treatment .tc

Avoid bending in front. Postural Correction- Sit Tall, Walk Tall. Extension Exercises x 15 times x twice daily - lying on tummy, take left arm up for 3 seconds, then bring it down, right arm up for 3 seconds, bring down. Bring right leg up, hold for 3 seconds, bring it down. Then right leg up and hold for 3 seconds and bring it down. Repeat twice a day- 10 times. Bhujang Asana -- Lie flat on your stomach, keeping the palms out, bend the neck backward, take a deep breath and while holding it for 6 seconds, raise the chest up. Release breath and relax your body. Repeat the exercise 15 times twice daily. Core Strengthening Exercises- Straight Leg Raised With Toes Turned Outward, repeat 10 times, twice a day. Apply Hot Fomentation twice daily.

It's highly likely to be linked with twisting of spine during squats with compromised ankle movements. It's also seen in persons with Scoliosis (sideways curvature seen in spine). The fascia gets inflamed and will prevent local movements like expansion of rib cage in forced breathing, triggering pain and spasm. Symptomatic relief can be achieved with moist heat (applying moist heat packs) or steam application ( with a towel placed in steam container) locally and rest for a week. If symptoms persist have an assessment with your physiotherapist so that the cause can be isolated and managed well.