Someone wanting to learn the trade has enough ethics not to break into other flats when wanting to practice picking,
Regardless of whether its emtpy or not you broke in to it, even if its never mentioned again and nothign was missing how would you feel if there was a fire but the person in that flat didnt get out to safety because you pissed around with the lock,
What stops the landlord saying theres a tv missing from that room and blaming you for it, he would be quite within his rights to,
The lock is owned by someone so if its not such a big deal why not go tell your landlord what youve done?
What you did is wrong, it is against the law and it makes you a petty criminal,