Multiattack. The Gorwahna makes two attacks: one bite and one with its stinger.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) piercing damage.
Sting. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 7 (1d10 + 2) piercing damage, and the target must make a DC 12 Constitution saving throw, taking 22 (4d10) poison damage on a failed save, or half as much damage on a successful one.