I've had it happen a couple of times and I think unless you really know what you're doing (and I don't in this regard) is to leave it until the next shed, perhaps increase the snakes feed and help it along to another shed. You certainly don't want to go damaging its eye trying to take it off.
I panicked the first time this happened to one of my snakes, but after some good advice (the same I'm recommending here) I let it go and it came off the next time round. I recommend that when the snake comes close to losing the skin the next time, mist the cage and get the humidity up to help loosen the old skin, you'll find it'll definately come off with the new slough.