is a very common and non-specific symptom, and it can certainly occur after smoking
It could be due to a minor lack of oxygen
, eye irritation
from the smoke, direct effect of thc, lots of things. All drugs, legal and otherwise, can have side-effects. If you get headaches, consider curtailing your use.
...Do you have a follow-up question? Consult Dr. Reidbord, a Psychiatrist with 30 years in practice: