Walking on the inside of your foot isn't fixed by forcing your weight to the outside — that makes it worse. The collapse is the body's way of acquiring a position it's missing. The foot needs pronation (arch down) AND supination (arch up, leg externally rotates).
Fold paper towels to about this thickness, or use wedges (better). Slide them under the INSIDE of the heel and first two toes of the working side — the outside of the heel and outer toes stay off. Feet hip-width apart, working foot one toe length forward.
Shift all weight over the working foot (pole through the nose down into the foot), neutral pelvis, knees ~10% unlocked. Gently push the passive knee forward to turn into the working side. At the gentle end range lock the knee (no hyperextension) and do another rotation. Feel a stretch in the back/side of the hip.