Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I think offhand that the first thing to do is to go back to that shop and complain and/or inquire. If they did it while servicing, they should undo it. That might even be covered by their service warranty.
They might even appreciate it as a correction or caution, who knows, to keep their work top-notch for all the next times that they service Nikon equipment.
Not forcing it is the right thing to do. Look for a lock-down screw, though, that might be keeping it from being adjusted, and if found, loosen it a little, then try again (and if there's no improvement, don't loosen it too much more.)
(Was the shop a Nikon Authorized shop? if not, I can get you listings for the ones that are authorized that are near you, if you reply with your zip code.)