It may be localised purpura
Cause may be slow trauma from pressure of jeans,infection some internal disease.
Blood investigations should be done to evaluate the condition.
Oral vitamin C
, vitamin K and antibiotics should be taken.
Thrombophob ointment should be applied.
Take rest and keep the affected leg elevated.
I hope you might be benefitted.
Still, you cosult dermatologist
Dr. Ilyas Patel MD