Taking the size of the follicle into consideration, it looks like ovulation may not occur as the ideal size has not been achieved. You may have to wait for the next cycle. Usually, during the course of follicular development, the follicle size increases until ovulation, when it usually reaches a size of 16-18 mm and ruptures. As the picture here is quite contrary, large follicle that has later regressed, it is suggestive of cyst
formation and not ovulation. Please discuss with your consultant for further care. Hope this helps.