The reality is that there is an enormous variation in the capacity of the different structures in the back to register pain which is why it takes an experienced practitioner to correctly diagnose your problem.
The discs themselves barely have a nerve supply, in fact only the outer most rim has pain sensing fibres, however if a disc is damaged it may well be responsible, perhaps through degeneration ?
When a disc bulges, it in effect presses on the surrounding soft tissue structures which are extremely pain sensitive.
There are two structures which are often effected by a bulging disc, the longitudinal ligament and the spinal nerve root, both are extremely rich in nerve supply stimulus.
The facet joints are also extremely sensitive structures and if the facet joints malfunction their own nerve supply will reveal this in the form of pain response.
Inflammation in the surrounding soft tissue can display referred pain to other structures which, if left unchecked may lead to severe muscle spasms.
Overload of the muscle tissue structures may also be the cause of back pain and we must remember that muscle strains and especially tears are usually associated with haematoma (bruising) which may not be so apparent if the site of the injury has originated on or around a tendon or ligament.
I have often heard people say, "stick a heat pack on it" and in some cases this may give some relief however, it is imperative that the issue is correctly diagnosed first for it may be that Ice would best be administered, for if one has torn muscle fibres, this is effect a bleed and one would not put a bleeding cut under a tap of hot running water, hence the heat pack could make your condition worse.
Contact Chris: 07887 898159