I'm 21 years old with thinning hair along my crown and left the side, could this be the start of alopecia? (Photos)

Noticed thin hair on the left side of the head along the crown of my head.Is this starting of alopecia or just because i used to have long hair with a ponytail hairstyle and maybe some hair follicles got damaged by this? Also my right side of my head is perfect.what are the neccessary treatment i can do to overcome this problem?? Thankyou