I had my house painted, the painter did not cover my motion detector light, he sprayed paint into the socket. I can see paint on the threads but not where the bulb touches the connectors. I screwed on a light bulb, and it still works. But is the light safe to use? Will the paint cause a fire? There is no way I can remove the socket, how will I go about cleaning it safely?
If the light is working, it should be okay without having to clean the threads. Personally, I would probably clean it...but thats just because, mentally, I can't allow that imperfection. Although, It would certainly be unnecessary if the light is functioning properly.
If you are like me and must at least try something, and you are not comfortable cutting the power and testing for a current before cleaning it, you could simply twist the bulb all the way in and out a few times in an effort to rub some of the paint off of the threads.
When I was a kid building a house with my family I noticed some of our recessed "can" lights had gotten paint spray into the sockets and covered the little "button" terminal. Before I'd even thought it through I put my finger in there to scratch the paint off.. yeah, the circuit was live. Obviously I lived to laugh about it, and I still occasionally work on circuits live.. but I recommend light socket cleaning be done with the power off. ;-)
The part of the threads where the light bulb contacts won't have received paint spray because they're on the side facing away from the spray source. If the button terminal at the bottom of the socket is clean then don't worry about it. Paint overspray into sockets happens often.