As his pain is radiating to other area and getting worse over the time so it suggests that venom is spreading.
So he needs to be seen by a doctor at ER.
Usually the initial line of treatment includes
Clean the area with soap and water and apply cool compresses on affected area.
Motrin 200 mg every 4-6 hourly.
If he has not had a tetanus shot within the last 5 years it would be a good idea to get one.
However his current symptoms(increased swelling,redness,pain) require an urgent medical attention.
I hope this helps.
Please rate me highly (Star 5 Great Service), if you are satisfied with our conversation.
If you have any further query then feel free to ask.
Bonus and positive feedback are highly appreciated.