That has happened several times at our house w/both bullies... Bella had gotten stung & her face swelled up so bad I ended up taking her to the vets. Winston did something to his eye & it was bulged out so bad I was afraid his eye was going to pop out!!! He ended up at the vets too... As long as you are watching him & the swelling is going down I wouldn't rush to the vets. It could be the grass, I've been wondering about my bully Winston too. Our grass was really tall last week, and I noticed he had a belly rash starting... I hope Kooper feels better real soon!!!