If you did do temporary or even permanent damage, what can you do about it ? Will worrying about it help you get through school ? Will it change your symptoms ?

You have far more important things to be busy with. Focus on the things you can have an impact on like being ready for school.

Sand has quite an abrasive impact. Your head ache could just be skin and the layers beneath the skin that have been traumatized by the sand. Lots of nerves in those layers.

I suggest you consider whether you can afford the rough waves.