Install lighting junction box directly over a stud?

I am replacing an old vanity lighting bar with two vanity lights. The existing wire is not secured in a junction box. My problem is that the location I need to install one of the new lights to center over the faucet is directly over a stud; so if I install a drywall junction box I will have to shift it an inch or two over, which I am afraid will result in the tabs and cut out protruding beyond the lighting fixture.

Any thoughts on how to handle this?