I would like to home my nema17 by making it collide into a rigid part of its housing (making it skip intentionally). Could that damage the motor in any way?
Or should I definitively use a homing switch?
I am using (this model Nema17).
NEMA17 (1.7" across the faceplate) is a size specification, not a motor type!
No, as long as you respect the maximum motor current, you're not likely to damage it. However, if you are using a driver that lets you control the current via software, you should lower the current to the minimum you need to avoid damaging anything else in the drivetrain: e.g., stretching belts or stripping set-screws. Over time, the vibration can also cause problems. Remember that you'll have to drive the motor into the stop for at least the maximum travel length because you don't know where you are at startup.
The homing position will be more repeatable if you use a home sensor.
Yes that's why I included a link to the specific model, if it would be necessary. 
I am using a DRV8825 driver board and I've correctly set the Vref (at a very safe value) with the screw knob on the top of the board, of that I am sure! It is all clear now. Thanks for your reply, much appreciated!!
What I meant is that for driving the motor into a stop, you'd want to set the current lower than it would be for normal operations. That reduces the strain on the driveline.
It's just a "nice to have" since I have yet to come across a hobbyist-level motor drive that has software-adjustable drive current.