First of all,I would advice you to quit smoking.
Headache may be associated with re-infection of root canal
Smoking can even worsen the periapical infection of tooth associated.
Please do visit a dentist
and get a clinical as well as x-ray evaluation done.
Depending on severity of infection,tooth has to be either extracted or re-rct has to be done.
Take complete course of antibiotics-analgesics prescribed.
Brush and floss your teeth daily.
Gargle frequently using warm saline or betadine
and stressful jobs.