What can I do about this bag / swelling under one eye? (photo)

I'm 31, male. I'm not sure what's going on, but I seem to have developed a noticeable bag under my right eye. I've had it for about 3 months now. I don't believe it was a gradual development, I'm sure it came on pretty quick. I've tried heat compress and eye creams but nothing helps.Can anyone tell me what it is and whether a surgical procedure is my only option? It's only noticeable when I smile/ grin. Not with a resting face. Sorry for the photo haha