How serious would a head injury need to be to warrant immediately avoiding alcohol?

I planned on going out drinking tonight but early this morning, around 10 am, I hit my head right at the temple on the corner of the windowsill. It was hard enough to produce a loud smack and cause me severe pain for about a minute or two but not hard enough to knock me unconscious. I have a slight welt on my forehead and a small cut that drew blood (though only a very little). I don't think it currently warrants visiting a doctor and I can't really afford to.

Everything I've read always assumes a concussion which I don't think I have. The only noticeable symptom I've exhibited is that shortly afterwards I went to sleep and have slept for about 6 hours and am still somewhat tired. I think that's fairly abnormal for me to be so tired but my vision hasn't changed, I recall everything immediately surrounding the event, I am very much coherent and can walk just fine. Would it be necessary to avoid drinking or might complications still develop that would be worsened by alcohol consumption?