Respected user, hi I evaluated your query thoroughly.
*It`s heat induced hypercirculation of any tributary of the forehead giving 
  rise to bulging in the vein with slight head ache.
*Don`t worry its of not that serious unless you are concious for :
 - maintain your hydration with plenty of liquids, lemon juice, coconut water, 
   green tea , coffee, juices, butter milk.
 - keep your BP , Blood sugar under control .
 - avoid direct exposure to excess sun for 1-2 days .
 - have adequate sleep of 8 hours.
 - avoid 
smoking / tobacco / abuse substances if using any.
 - can take simple 
analgesic like 
acetaminophen for headache.
  Hope this clears your query.
 Thanks for using Health care magic & keeping trust in our medical services.
 Wishing you fast and speedy recovery from the same.
 regards dear take care.