It is normal for the temps to go up a little bit. I notice that our humidity usually does too.
How many degrees did it go up? If you are worried you can always open a window (or depending on what type of incubator you have) open it a sec to bring it down.
Now, there are others that will tell you to not ever, ever, ever, open the incubator once the hatch has begun. Again if you are worried, just adjust the temp a tiny bit.
You really have to get to know your incubator and what works.
Happy Hatching!
Deb