Hitting any obstacle with the front wheel has always a worse events development potential compared to hitting the same obstacle with the rear wheel: one can loose control over the bicycle and fall down. Achieving the same result after a hit in the rear wheel is also possible, but much less probable (however, another possibility to be thrown out of saddle if one sits too tight on it arises). Even if the rear wheel skids or destroys itself, you will still regain much of control so that you are more likely to make a controllable stop.
Because of this, if no other alternative is available (braking, avoiding, hoping over etc.), I would recommend lifting the front wheel. If, after the wheel is over the obstacle and you still have reaction to unlift some weight from the rear wheel, do it. Doing so will help the rear wheel to bump over the obstacle and minimize risk of wheel damage. If you do not do that, it is fine as long as you are not sitting fully on the saddle. Otherwise the rear wheel bump will have chance to throw you into air. Standing on the pedals is recommended during the whole time of attack.
I feel like I don't feel so much the bump
It is actually good that you do not feel the bump — it means you have overcome it without creating a risk to loose control. If you were standing on pedals, it were your legs that absorbed the bump for you. If you sat fully on your saddle, the whole kinetic energy change caused by the bump would have been transfered to your center of mass, effectively launching your whole body into flight.
if I do that but what matters is if I'm damaging the wheels.
Yourself avoiding undesired flight matters more than your wheels. Wheels are built to withstand bumps, do not think about them too much.