|There is probably absolutely nothing wrong with your bios. |
It sounds like your built in display is failing, or you have damaged wiring between the display and the video adapter, probably right where it passes through the hinge area.
Both are common problems after your laptop has been used a lot, or at any time if the laptop has been damaged, e.g. by dropping it or dropping something on it or by spilling liquid on it.
Usually there is nothing wrong with the video adapter. In that case an external monitor will work fine.
Some laptops will automatically enable a display on an external monitor. On others you must press a key combo to toggle the display - to external, built in, or sometimes both of them - see the User's or Owner's manual for your model.