Looks like what i call a swelling knuckle. I dont know whats its called just made up something. I see it alot when lsting. What i think it is is the plant is strengthening the joint to support the weight of the branch. Kinda like if you are gonna be lifting heavy shit all day you want to be in shape otherwise you couldnt do the job. I think its just the plant bulking up. Like i said i see it all the time. Maybe someone will pipe in that can give you a real name haha Are you sure its gooey? If its what im talking about it should be hard.