Safe to have 1 mg Finasteride from 3 weeks after hair transplant when I've had a gynecomastia surgery 10 days before transplant?

If you have a history of gynecomastia you need to discuss your decision to take Propecia with your surgeon.  You need to understand all the side effects (one of which is gynecomastia) and weigh it against the benefits.

what is the reason for that?.You may have Post-finasteride syndrome in long term usage, occurs in men who’ve taken finasteride to treat hair loss by a chance of %4-5. That may causes some symptoms include: loss of libido, erectile dysfunction, depression, suicidal ideation, anxiety, panic attacks, Peyronie’s disease, penile shrinkage, gynecomastia, muscle atrophy, cognitive impairment, insomnia, severely dry skin and tinnitus. The condition often has a life-altering impact on victims and their families, such as job loss and the breakup of marriages and romantic relationships..

If you had Gynecomastia from a non-finasteride related cause, then taking the drug should not produce a recurrence of the problem for you, even at traditional doses