Need a photo really as there are many different types. It could be that the side springs that hold the body of the light fitting in place, have come off as you pulled it down? If so you can buy replacement springs from toolstation.
Normally you apply slight pressure to the surface of the bulb pushing it towards the back of the fitting and twist with finger tips to left or right,
If it has not been changed for a while they are known to become a little more difficult to release,
you may have damaged the outer chrome ring of the light if it will not stay up ?!
Regards
SF.