Mild gynecomastia. Can laser work in such a case?

There is no lotion or potion that can treat gynecomastia. I would suggest that you seek a second opinion from another board certified plastic surgeon with a lot of gynecomastia experience. If he or she also tells you that nothing can be done surgically then you have your answer. Best of luck.

There is no lotion, potion, cream, ointment, exercise regimen or specialty diet that will change gynecomastia. It is only treated with some form of liposuction and tissue removal as indicated.
The Internet is full of "magic cures" for gynecomastia because there is a market for them driven by men who would prefer to not have a procedure when they are able to take care of it themselves. 
The reality of the situation is that it won't go away unless it is removed. The great news is that the procedure works really well and is relatively simple and straight forward in experienced hands.

You need a surgeon with experience with gynecomastia surgery.
You can have ultrasound to see the amount of gland you may have.