SOLVED
The phone comes with a protection attached over the loud speaker but beneath the back cover. Very much similar to the thin anti-scratch protection on the display. This one should be removed so there should not be any harm in what you've done. 
As for warranty questions you should contact the Romanian Sony support office.
http://www.sonymobile.com/global-en/support/contact-us/country/ro_RO/
I can however confirm that any phone bought in a EU/EFTA country should have valid warranty in all of the other countries that are members of these unions.
The e-shop you bought it from, do you know in which country they are registered?
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