What should I do if the screw head broke off while I was trying to tighten it?

If the screw head broke off while you were trying to tighten it, you can try using a screw extractor tool to remove the remaining screw from the surface. If that doesn't work, you may need to drill out the screw and re-tap the hole for a new screw. It's important to be careful and patient to avoid damaging the surface further.