Thanks for sharing your concern.
It could be a case of dry socket
which is secondarily infected.
How about your medical history,like have you checked for BP and diabetes
.?Are you taking any other medication like prolonged antibiotics or steroids?please mention that too.
it also shows that your alveolar bone(which holds the tooth and its roots) has not healed properly
leaving a gap in between,on secondary infection it has turned painful.
Further i would suggest you to visit your dentist
once and get it examined clinically.
so that suitable antibiotics and analgesics can be started to prevent further infection.
Meanwhile maintain good oral hygiene
as it helps in healing process.
Hope it helps.