MaxLB

When I was washing my car today I noticed a spot on the driver's door where the paint is bubbling. It's about the size of a quarter and inside the weatherstripping. I clean my car fastidiously, so I know this was not there before about 3 months ago (last time I washed the car due to COVID not driving). In SoCal, where it almost never rains, can this be rust? Why in such a protected area? Will try to go by the dealer this week and have them look at it.