That's about it. Supposed to flush the sting in water as hot as you can stand and if you start having any reaction to the venom, get to the ER. The sting is supposed to be very painful to so, just use caution and know where he is in the tank at all times while maintaining. Or have a second pair of eyes with you while working in the tank. Great fish with lots of personality. Good luck with your new lion.
Just wanted to add something here. This is a paragraph taken from the conscientious Marine Aquarist book by Robert Fenner.
Though not as toxic as their stonefish cousins, lion stings must be taken seriously. Swelling, soreness, localized pain, respiratory and cardiac distress, and other collateral shock manifestations go with these events. Ringing your local poison control center and submersing the site with water as hot as you can tolerate are immediate emergency actions to take. Most sting victims recover quickly without treatment but have to suffer hours of pain that typically leave a lifelong impression and respect for natural venoms.