If the small area of the headlight has trapped the moisture, then you can simply fix it without removing the headlight unit.
Clear Blocked Vents. Find the vents of your vehicle?s headlights. They may be different depending on the make and model of a vehicle. As we discussed above, one of the common reasons for minor condensation is that the vents are blocked.

All you need to do is wipe off any spider webs, dust, or debris that you see blocking the way. You can also blow out the same with compressed air. Keep in mind that you don?t push or blow any dirt inside the headlight unit.

Use Hairdryer. You can also use a regular hair dryer to put some heat into the headlight unit. It will easily remove the moisture with the evaporation process. Simply blow the hairdryer into the vents and after a few minutes, you should see the result. look at this site

Moderate Moisture
If your headlights are moderately condensed, then you may use pressurized air from a vacuum cleaner. This tool can be used not only to make the surface dry with heat but also to clean the vents if they are blocked with any debris, dust, or spider webs.