if you get a sticker thermometer for the side of the bucket, you'll have a more accurate reading of the wort than what you have now... it won't be a dead-on reading as the wort in the middle of the bucket is hotter than the outside, but it's better than a reading of the ambient environment.
opening up the bucket and taking temperature can lead to both oxydation and infection (depending on who you ask)... so unless you're putting the bucket in a swamp cooler or fermentation chamber as a result of your reading, I'd just let this batch stay the course and adjust your process on the next brew...
oh, and do get one of the sticker thermometers for your bucket... they're about a buck each
