@Chirag S. nothing will happen if they open the bonnet and spray the engine bay. Years ago some cars used to have a problem starting if water was sprayed in the engine bay with high pressure as water used to get into places it should not but with current cars it is not a problem.
I pressure wash the engine bay on my Grand Cherokee every alternate week and have been doing this to my cars for the last 10 years at least. If you do have access to an air blower, use that to blow out the excess water after the wash or ask the service center to do it if you are getting the car washed out.
Besides it being a good habit to keep the engine bay clean, it also helps you detect any new leaks that need your attention.