I'd reset the bios to the default settings and start over. PWM fans are not designed to be used with DC setttings, so you MIGHT have damaged the fan especially if it's a cheap model fan with poor PWM design. DC controls speed by changing voltage lower or higher. PWM changes speed but pulsing the 12v signal, not by changing voltage. PWM fans are not generally built with electric motors that are designed for use with variable voltages and much like any motor when there is not adequate voltage or too much voltage, it can harm the motor.
I wouldn't think it would be damaged if you only ran them that way for a short time, but again, it's hard to say and probably depends on the quality of the fan.
Try doing a hard reset of the bios. You'll have to reconfigure any custom settings afterwards.
Power off the unit, switch the PSU off and unplug the PSU cord from either the wall or the power supply.
Remove the motherboard CMOS battery for five minutes. During that five minutes, press the power button on the case for 30 seconds. After the five minutes is up, reinstall the CMOS battery making sure to insert it with the correct side up just as it came out.
Now, plug the power supply cable back in, switch the PSU back on and power up the system. It should display the POST screen and the options to enter CMOS/BIOS setup. Enter the bios setup program and reconfigure the boot settings for either the Windows boot manager or for legacy systems, the drive your OS is installed on if necessary.
Save settings and exit. If the system will POST and boot then you can move forward from there including going back into the bios and configuring any other custom settings you may need to configure such as Memory XMP profile settings, custom fan profile settings or other specific settings you may have previously had configured that were wiped out by resetting the CMOS.