Thanks for your query
You seem to have developed severe sun burns due to excessive sun exposure.
You need to apply a topical steroid
cream over the affected area atleast twice a day over the affected area inorder to decrease the inflammation.
And take some oral antihistamines like levocetrizine once a day.
In addition, you might need a course of oral steroids
since the area involved in your case is quite extensive. I would recommend that you should see a nearby physician for the same.
You should use a sunscreen (spf>26) everytime before you go out in the sun in future.
Regarding a sunscreen, it is important that you should apply adequate amount of sunscreen over all the exposed areas before going out in the sun.
It should atleast be applied 30 minutes before any kind of sun exposure and it should be reapplied every 3-4 hours in you stay out in the sun.
Hope it helps
Dr Geetika Paul