Please elaborate on what kind of surgery you have underwent and assuming you are talking about wisdom tooth impaction , it depends upon the amount of trauma caused in the region , please visit your dentist he will place you on stronger painkiller and muscle relaxant and antibiotics ,duration of pain can vary from a day to a month , and in cases of dry socket it can extend more , wishing you a speedy recovery

It will settle down. You have to be patient. Meanwhile you can gently move mildly warm salt water in the mouth on the affected side 4-5 times. This will help.Eat healthy protein diet. Avoid spicy, sour foods.

It should be fine in another 2 days. Continue warm saline rinse.

This usually happens with such surgeries. Your dentist can be of real help now to  in managing your mouth opening. Visit him and with his consent extend your medications for few days