Extra suncream and maybe buy local, sometimes the local suncream can be better for their ozone. If he seems uncomfortable maybe a half dose of paracetamol if you don't want to give a full dose. Keep the aftersun going and hopefully he'll be ok. You could also potentially go to a pharmacy if he seems uncomfortable they can be great when abroad, I did thay in Turkey when my baby was constipated and I bough glycerol suppositories from them. They may have some magic tonics
Long sleeve shirt, aloe and water. That's all you can do now. Does it hurt? Keep applying the aloe if it dries quickly