See if you can wedge something thin under the head/washer (piece of cardboard, old credit card) that might exert some pressure & allow the bolt to be removed.
Here's the link to the online repair manual. Good luck!
https://www.newtis.info/tisv2/a/en/
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2015 BMW 228i in EstorilBlau II Metallic / Terra Dakota Leather - 6-speed manual, M Sport Package, Cold Weather Package, Lighting Package, Premium Package, Harman Kardon premium sound, Anti-theft alarm system, Blue Metallic Matt Accent Moldings, Aluminum Hexagon Interior Strips, Anthracite Headlining