If your third molar removed surgically ( incisions and bone cutting) then cause of swelling (inflammation) is surgery. But it was gradually subside after 48 hours. In your case, 4 days is much more. So may be some other possibilities of causes. After tooth removal instructions proper followed by you like ice pack for upto 24 hrs then after warm saline rinses 6-8 times daily.
Maybe the possibility of broken root or tooth particles or improper curettage(wound cleaning), so please verify it. Sometimes pain may be due to upper wisdom teeth.
But you told that you had a crown next to third molar; please consult for that tooth. Sometimes it may be caused.
Irregular medicines taken by you which are prescribed by your dentist and advised instructions not followed by you.
Next Steps
So please consult with dentist and rectify the solution