Thank you for the reply.
I think you need to start with talking to your vet to get a better idea on what they thought they were dealing with the first time. If it was a cyst, was it infected and when they did surgery, did they attempt to remove it? If not, it is not a surprise that it recurred. Cysts can occur anywhere, and can fill up with discharge, rupture and become infected. If not removed, even if the infection resolves, eventually it will happen again. There are a lot of structures in that area of the body including lymph nodes, salivary glands and such, so if it wasn't a cyst, perhaps it was some other structure, but they should have an idea.
Of course, it is possible it was all just a abscess, but if so, why did it recur? Abscesses only usually form if there is a unhealthy tissue or infection, so if this is in the same spot as previous, there must be a source of infection that wasn't removed. You can tell if there is a root tip infection/abscess without an xray, but that doesn't sound like the correct location. It could be related to his ears and middle ear infections can lead to abscesses on the cheek and neck if severe enough. Make sure someone looks in his ears and he may even need skull xrays if his eardrum cannot be visualized.
I hope that gives you some things to discuss with your vet.
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.