popping of big toe, pain & misdiagnoses

Please help!
I hurt my left foot about a year ago.
Originally I thought I hurt it in a Yoga class, but now I believe I hurt it by popping my left big toe (normal popping like people do with their back &/or knuckles).
I went to a podiatrist, had x-rays & an MRI and nothing showed up (no fractures, etc), but a year later I still have pain.
The pain is not so intensive that I cannot walk, but a dull, persistent ache.
Pain is mostly in the big toe joint (I cannot always bend the big toe in the normal full range of motion), and sometimes in the middle inside of the ball of my foot.
The big toe & middle inside often become sore or ache after lots of walking or general exercise (and the middle inside is sometimes inflamed I think).
My podiatrist orginally thought it was my sneakers, which I changed, but has obviously not helped.
Any advice or push in the right direction would be MUCH appreciated.
Thanks!Wendy