Beezrat Hashem, I quote from Britannica online encyclopedia:
Pain is a complex experience consisting of a phsyiological and a
psychological response to a noxious stimulus.
Pain is a warning mechanism that protects an organism by influencing
it to withdraw from harmful stimuli.It is primarily associated with
injury or the 'threat' of injury.
Pain responses are learned in early childhood and are affected by
social, cultural, psychological, cognitive and genetic factors among
Chronic pains are attributed "to a functional disorder or persistent
irritation of the nervous system"
Pain, in other words, is your feeling of 'there is something wrong and I have got to do something about it'.The 'what to do'however, varies.
At times the call is to act and at times the call is to convince yourself of having done your part and thus vier your thoughts elsewhere and let the pain subside saying 'message heard'.
A person thereby need not have pain even without administering any painkillers.One can choose to persuade himself of his playing his part already and thereof not feel any pain for there is no message for him via the pain being sure that he has done his part.
Now that we clarified somewhat the essence of pain,truthfuly speaking, administering painkillers may be comparable somewhat to one ignoring the root and placing a bandaid in its stead.Although it is not expected of anybody to strive towards that direction, however one who's heart is telling him 'perhaps you are ready for that'would do a comendable act, as for him to(soak up or)receive painkillers would vier from an opportunity of growth on that account.
Although we don't foresee one to acquire the strength of psyche and personality to conform and yield himself to compliance gare, and thereof have pain when not administering painkillers, nevertheless having let oneself decide on his plan of action and be at ease with the moment's condition and hereby put effort into a step forward towards complacency and contentment by enduring his lot that in itself a fulfilment of life's objective and deserves to be lauded.
Being that pain is there as a tool to show you how to (perform,and yes performing will also get you somewhere or) operate from there, it is not considered tsaar but rather something joyous and if you take advantage of the message and do something about it this is precisely what you were asked to do.
Therefore one who chose to decline painkillers and face it wholeheartedly which when done fully would make him pain free, although he has not reached that state, nevertheless did grow and arrive closer to life's objective of Bitachon and serenity, and has cultivated that attribute in partialness into his psyche.
His pain was there but was advancement heading pain.
This is not equivalent to someone withholding from wine which Chazal condemn, being that this situation was brought upon him rather than him putting himself into the situation.
I thereby conclude that may one choose the no painkiller path he chose an attaining path and did get nearer to his destination.Yes, he was in 'pain' but did 'obtain' a stronger 'sane'.