Consult a dentist and get a radiograph taken. From the sound of it, it looks like a n abcess has formed. Now we to know exactly where the abcess is. Only then we can get it treated. If it is in the gums then we have to simply drain the pus. If it is under the tooth, we have to think of extraction or RCT. It can also be due to something else entirely. The only way to know it is to get a radiograph taken, and them a treatment plan can be formed accordingly.
Next Steps
Consult your dentist
Health Tips
Don't delay as it will lead to other complications.