Its usually caused by excess stress from sudden bending upwards of the big toe.
Have you had anyone look at the way you are striking the ground?
You may be landing too far on your toe.
It can be tough to heal because every time you walk you put additional pressure on the sesamoid bone.
You need to manage the chronic inflammation.
Have you had anyone look at your walking pattern or your the shoes you are wearing?
Both can impact the situation.
Have you had it looked at? or seen a PT?
Strengthening your feet can help.