I don't think it's possible to get an ID from that picture.
If you see any spiders that you are not happy about, take a sheet of paper, roll it into a cone, fold over the point, so they can't escape. Scoop them up & put them outdoors. I also have a soft plastic pop bottle that I have cut the bottom off, put the lid on and you have a great spider catcher.
False widows aren't really any different to a number of spiders you might find in your house...yes, they are able to bite (unpleasant, but symptoms will pass in a couple of days, keep an eye out for any infection - as with any bite/sting/cut), but they are actually quite docile & not aggressive. They run & hide given the option. The females often stay around one spot.
If there is one (of any species) then there will be others...but Steatoda nobilis (the noble false widow) tend to like a bit of space, it is unusual to find adult females in close proximity to each other...sometimes they may have a male hanging around.
So, in short, I don't know if you have a false widow. but even if you did find one indoors, just put it outdoors.