Flat warts on face. Treatment for this?

Last year I found small growths on face (around the cheeks mostly). When I went to the doctor told me it's flat warts caused due to HPV. He prescribed Retino A 0.05 but even after a whole month the warts didn't go away. Then I visited him again and he recommended laser treatment which I agreed to. The warts disappeared after the treatment but after a few months they came back again. I started using Retino A again as soon as I found them reappearing. It worked a little this time but after continuous use of this cream my skin started to get damaged. It got corroded and I had to stop using it. The warts again started to grow. It's been more than a year now and my face is still battling these warts. Retino A is not working anymore. Is there any other permanent treatment for this?