Paint issues

[Kodjo]

I had my car repainted last winter. I did the disassembly, sanding, and bodywork myself, but a friend handled the spraying. Now, after a long period of heavy rain (the car is parked outside), bubbles are forming in the paint. Luckily, it’s only in one spot—right under the rear quarter window on the driver’s side. As far as I remember, there wasn’t anything special about that area when the car was stripped down. Any advice on what to do?