I've accidentally passed out from breathing helium from a 10-foot weather balloon. It's not painful at all, actually slightly pleasant. A lack of oxygen absorption doesn't directly cause discomfort.
Increased blood CO2 is the main cause of discomfort from holding your breath for a long time. This is why hyperventilating to bring your CO2 level down helps you hold your breath longer. (The light headedness from hyperventilation is a consequence of low CO2.)
I don't believe cyanide particularly increases blood CO2 prior to loss of consciousness. Also, I'm told carbon monoxide poisoning isn't particularly uncomfortable, and also interferes with oxygen transport. So, your proposed mechanism seems unlikely.
Someone else here mentioned that cyanide poisoning is painful due to lactate production: that muscle burn from working out, but presumably worse, building until death.
Other tissues besides muscles may also have lactate receptors; I'm not sure. If that's the case, your whole body may have that workout burn.
Increased blood CO2 is the main cause of discomfort from holding your breath for a long time. This is why hyperventilating to bring your CO2 level down helps you hold your breath longer. (The light headedness from hyperventilation is a consequence of low CO2.)
I don't believe cyanide particularly increases blood CO2 prior to loss of consciousness. Also, I'm told carbon monoxide poisoning isn't particularly uncomfortable, and also interferes with oxygen transport. So, your proposed mechanism seems unlikely.