Hi.. Thanks for the query.. Feeling of pain under the jaw with a ball like structure under the jaw while swallowing is appearing to be a swollen lymph node.. It is commonly seen in case of recent or ongoing infection.. At times it can be simply an infected lymph node with no visible signs of infection.. So my suggestion is to consult an Emergency room and get him evaluated.. He can be advised a short script of antibiotics like Amoxicillin and if there is pain painkillers like Acetaminophen or Ibuprofen can also be advised.. Along with it also do alternate warm and cool compresses over the painful area.. Hopefully the symptoms will resolve in a week.. Hope this helps.. Regards. Dr.Honey Arora.