Hot water and pull. It may take some effort to get it off. I have had tubing get stuck on my immersion chiller and it took a bit of pulling to finally get it off.
This. twist back and forth until it loosens, don't just pull, which only stretches the tubing and constricts it more. I've had good luck with pushing a little while twisting just to loosen it up.
I bottled my first batch this weekend and had the same problem. I ran hot tap water (as hot as I could get it) over it for about a minute and with a little twisting, it came right off.