How to fix a Canon s45 lens cover?

My canon powershot s45 seems to have a problem with the sensor in the lens cover. When I try to close the cover, the lens will not retract back and remains out. The camera still takes pictures and seems to be working fine in every other way - I just have to take the battery out if I want to turn it off, and carry it around with the increasingly scratched lens sticking out.
The only way I can get the lens to retract is by plugging the camera into my laptop, as if to download photos.

Any ideas about how much this type of problem will cost to fix, or wether I can fix it myself?

Thanks