I have cubitus valgus in left hand as a result of old fracture , one month back i treated with ulnar nerve transposition , can i treat my elbow angel?

Not usually advised: Unless you have significant functional problems like loss of motion of the elbow correction is most commonly not recommended. To do so would involved a large incision, cutting and re-aligning the bone and putting in plates. It would probably take 10-12 weeks to heal and there is a significant risk of nerve injury.

Cubitus valgus elbow: Angulation can place "tension" on the ulnar nerve and result in what is at times referred to as a tardy ulnar nerve palsy. Transposition is recommended to relieve that tension on the nerve. If the fracture is very old it is usually not wise to treat the deformity now especially after or with nerve surgery but of course its never an absolute, speak to your surgeon about your concerns.

Valgys: If chronic, few options other than osteotomy or just living with it.

Cubitus Valgus: when the elbow angle is such that the hand goes away from the body with the and facing forward as the arm is at the side, is not often corrected if it due to a boney injury. the late affect can be a so called tardy ulnar nerve palsy. After nerve transposition to attempt osteotomy would not be strongly advised but even then the issue is often cosmetic when no ligaments are truly involved